Australian Simmons, the first overall pick in the 2016 NBA Draft, appeared in his second straight All-Star Game in Chicago at the Weekend.
The 23-year-old is averaging 16.9 points, 8.3 assists and 7.9 rebounds per game for the 76ers, while he also leads the NBA in steals.
Earlier in this campaign he drained his first regular-season three-pointer - with Simmons' shooting from beyond the arc often used as a stick to beat him with - and 2007 NBA MVP Nowitzki believes that is the only facet of his game preventing him from moving into the elite echelon.
"I love Ben. I got to meet him a couple of times. His potential… the sky's the limit," said Nowitzki, who was speaking at the Laureus Awards in Berlin, where he won the Lifetime Achievement prize.
"He's super, super athletic, he's got a great touch. He sees the floor, gets his guys involved. Eventually, I think we all know, he needs to improve his shot.
"If he improves his shot he can be one of the best in the league, best in the game.
"Just right now people are playing off him a little bit and making him shoot.
"He's got the touch, the feel for the game that if he works hard, keeps improving the way he has – he's still young – he's going to be fun to watch for a long, long time."
Nowitzki brought the curtain down on his decorated 21-year NBA career after last season having been named to 14 All-Star Games and also winning the 2011 NBA Finals with the Dallas Mavericks, where he spent his entire career.
Despite Nowitzki's departure, the future looks bright for Dallas thanks to two other Europeans - 20-year-old Slovenian Luka Doncic and 24-year-old Latvian Kristaps Porzingis.
Doncic has already taken on Nowitzki's mantle as Dallas' star and he was named as a starter for the All-Star Game in just his second season.
"Amazing," Nowitzki added of Doncic.
"He was voted a starter at 20 years old. He's been so much fun to watch and hopefully he'll stay in Dallas for his whole career and we'll have a lot of fun watching him, hopefully for a long, long time.
"The way he plays, the way he reads the game, the way he scores – he's a great all-round player. He's super fun to watch.
"They're young still. Luka's only 20, Kristaps is 24. Hopefully those guys can build something and be together in Dallas for a long, long time and play on a high level.
"Of course, eventually they would like to bring a championship to Dallas, that would be amazing. We'll just see how they play off each other and grow together."
On receiving Laureus' Lifetime Achievement Award, Nowitzki added: "Of course it's a great honour to get the award for my lifetime achievement.
"I played more than 20 years in the NBA. I was trying to move the game forward.
"It's nice to feel that you're respected and accepted for what I achieved during my career. For me it's a huge honour. I'm glad to be here."
Bryant, 41, and his 13-year-old daughter Gianna were among nine people killed when a helicopter crashed in Calabasas, California on Sunday.
The five-time NBA champion spent 20 seasons with the Lakers, a record for longevity with a single team that stood until Nowitzki entered his 21st campaign with the Dallas Mavericks in 2018-19.
Nowitzki, now retired, memorably led Dallas to a series sweep of Bryant's Lakers in the 2011 playoffs, en route to the franchise's sole championship.
The Mavs announced they would retire the number 24 jersey Bryant wore during the second half of his career and their favourite son shared his sorrow in a social media post.
"This is hitting me really hard," Nowitzki wrote in a statement addressed to 'Mamba'.
"I will always remember coming home after games so I could watch you dominate the in the fourth quarter! You inspired so many around the world, including me.
"You will always be missed. You will always be remembered. You will always be loved. Rest in peace with your angel Gigi.
"Deepest sympathies to Vanessa, the girls and all the friends and families of the lives lost today!"
German forward and 2007 MVP Nowitzki was drafted two years after Bryant and the pair went on to play a combined 2,868 regular season games.
Nowitzki, a 14-time All-Star, spent his entire NBA career in Dallas, winning a championship under Carlisle in 2011 when he was Finals MVP.
But the 2007 MVP retired in 2019 and so was restricted to the role of spectator as the Mavs looked to build on a Game 1 first-round playoff win on Tuesday.
His presence was enough to inspire his former team, too, with the German pictured with current Mavs superstar Luka Doncic following the game.
Doncic led the way with 39 points in an impressive 127-121 win, improving his postseason average to 32.0 points per game. That is the highest mark of any Dallas player regardless of games played, with the top spot previously belonging to Nowitzki as he scored 25.3 points across 145 playoff appearances.
There is a long way to go before Doncic can think about repeating Nowitzki's Finals run – a Miami Heat series in which he averaged 26.0 points – but the support of the team's greatest ever player is a boost.
"I saw him and [wife] Jessica in the hotel yesterday," said Carlisle, Mavs coach since 2008.
"It gives you a profound lift when you're in between the first two games of the playoffs and you see that playoff warrior who we've been through so many battles with.
"He said that he was going to be coming to the game, which was great news.
"And I certainly believe that him being there tonight was a lucky charm for us. It never hurts, never hurts."
Although Doncic was the obvious star once again, there was also a big performance from Tim Hardaway Jr, who contributed 28 points and made six attempts from beyond the arc. Both were career playoff highs.
Hardaway said: "[It was] 2-0 when Dirk gets in the building, I'll tell you that.
"Yeah, Dirk, we saw 'Dirky' earlier in the day, we knew he was there and we were happy we were able to pull out a victory.
"It's still a long series and the job is not done at all. It's just creeping into what we can become and we've just got to keep on focusing in and locking in."
Legendary coach Popovich has won five NBA titles with the San Antonio Spurs, and is one of a number of people named as a contender in their first year of eligibility.
Popovich is a perhaps surprise inclusion, with it previously unknown when he would qualify to be recommended for the honour.
Other potential inductees include Pau Gasol, Tony Parker and Dwyane Wade, while the 1976 U.S. Olympic women's basketball team also made the list.
The finalists for the class of 2023 will be announced on February 17 during All-Star weekend, before the final nominees are named on April 1 during the NCAA Final Four.
The players will then be enshrined on August 11 in historic Springfield, Massachusetts, where the sport of basketball was invented.
The San Antonio Spurs coach has won five NBA titles and more games than anyone else in the history of the league, with 1,363 regular season victories and a further 170 in the postseason.
Headliners joining Popovich in the class of 2023 are Dirk Nowitzki and Dwyane Wade, as well as two players who played under 'Pop' in San Antonio, Tony Parker and Pau Gasol, and his former assistant and San Antonio Stars player Becky Hammon.
Popovich is coming towards the end of his 27th season with the Spurs, sitting in 14th place in the Western Conference with a record of 19-58.
In better days though, Parker won four championships with Pop at the Spurs, while Gasol makes it more for his success with the Los Angeles Lakers, where he won two titles.
Dallas Mavericks legend Nowitzki won the 2011 championship and is sixth in the NBA's all-time scoring list, while 13-time All Star Wade won three titles during his 13 years with the Miami Heat.
Hammon – a six-time WNBA All Star – worked under Popovich in San Antonio between 2014 and 2022 before becoming head coach of the Las Vegas Aces in the WNBA.
Wade, Nowitzki, Gasol and Parker are all first-ballot selections after playing their final seasons in 2018-19, while it was also Popovich's first time on the ballot after previously declining Hall of Fame consideration in recent years.
Hammon's elevation was also considered simply a matter of time, with the six-time WNBA All-Star, former long-time San Antonio Spurs assistant and 2022 WNBA championship-winning coach with the Las Vegas Aces having put together a stellar resume since turning pro in 1999.
With Hammon's ties to the Spurs, it figures to be a special night for San Antonio fans as Parker and Popovich are enshrined, joining fellow linchpins of their dynasty Tim Duncan and Manu Ginobili after their inductions in 2020 and 2022 respectively.
Popovich coached the Spurs to all five of their NBA titles – 1999, 2003, 2005, 2007 and 2014 – while Parker contributed to the last four after arriving in 2001 following an impressive youth career in France.
The six-foot-two point guard made six All-Star teams, and was named to the All-NBA Second Team three seasons in a row from 2012-14 as the Spurs battled LeBron James' Miami Heat in a legendary rivalry.
His number nine jersey was retired by the Spurs, as is Nowitzki's number 41 jersey with the Dallas Mavericks.
Nowitzki, who for a long period was European basketball's biggest star, brought the Mavericks their only title in 2011 as he took down the Heat in James' first season there.
The German was named league MVP in 2007, and went on to make 14 All-Star teams, while earning 12 All-NBA selections, including four on the First Team in the space of five years.
While both Popovich and Nowitzki could headline a Hall of Fame class in any given year, that honour may go to Wade, who was the architect of all three of Miami's titles in 2006, 2012 and 2013.
Drafted in 2003, Wade ended up carrying the Heat – alongside Shaquille O'Neal – to their first ever championship in only his third season.
It was the beginning of a run that saw him make 14 All-Star teams, eight All-NBA teams, and three NBA All-Defensive teams as he rivalled James and Kobe Bryant for the status of best player in the league in 2009 and 2010.
While Wade may have been at his peak in 2009 and 2010, both of those seasons ended with Gasol lifting the title with the Los Angeles Lakers.
Gasol spent just six-and-a-half seasons in Los Angeles, but it is where he will be most fondly remembered after making such a profound impact that he recently had his number 16 jersey retired into the rafters alongside running-mate Bryant.
Adding to his NBA resume was his spectacular international play, where he became the all-time leading scorer in EuroBasket play, averaging 20.4 per game in 58 appearances for his country, while also carrying Spain to their first ever FIBA World Cup gold medal in 2006.
