Sixth seed Jason Kubler made light work of 39-year-old Spaniard Fernando Verdasco in the first round of the Houston Open while Americans Steve Johnson and Denis Kudla advanced on Monday.

Kubler and Verdasco endured a 71-minute first-set tussle, which the Australian edged 9-7 in a tie-break before dominating the second frame, dishing out a bagel in 29 minutes to win 7-6 (9-7) 6-0.

World number 71 Kubler progressed to the second round where he will take on Colombia's Daniel Elahi Galan who defeated China's Zhang Zhizhen 6-2 6-3.

Johnson set up a second-round clash with American compatriot and top seed Frances Tiafoe after getting the better of Facundo Bagnis 7-6 (7-5) 1-6 6-1 in one hour and 55 minutes.

USA's Kudla also progressed with a hard-fought 6-4 4-6 6-4 victory over Australia's Aleksandar Vukic in just under two hours.

Dutchman Gijs Brouwer won 6-4 6-4 over Aleksandar Kovacevic, setting up a meeting with big-serving fourth seed John Isner.

Andy Murray stumbled out of the Melbourne Summer Set tournament after a first-round defeat to Argentinian Facundo Bagnis.

In his opening ATP Tour match of the year, three-time grand slam winner Murray slipped up 6-3 5-7 6-3 against Bagnis, a player who began the year with a 30-59 win-loss career record.

Left-hander Bagnis rose to the occasion on Rod Laver Arena to earn the scalp of the former world number one.

Murray, down at 134th in the rankings after another injury-hit year, is looking to make headway on that front in 2022 under new coach Jan de Witt, so that he can avoid having to take wildcards into tournaments.

He was allowed into this tournament by that back-door route, and has also been confirmed for an Australian Open wildcard, but the Scot could not find the form that saw him beat Rafael Nadal at an exhibition event in Abu Dhabi in late December.

Bagnis said of his win: "In the beginning it was a pleasure to play against Andy and right now to beat him is amazing. I'm really happy."

He added, according to the tournament website: "Yesterday, I came to see the stadium, to see it all around because the atmosphere is different when you play on any court outside… I enjoyed it a lot. It was so good for me."

Nadal was also back in action on Tuesday, playing his first match on the main tour since August as he teamed up with fellow Spaniard Jaume Munar for a doubles win.

A foot injury meant Nadal's 2021 season ended early, but he warmed up for singles tests that lie ahead by joining Munar for a 6-3 3-6 10-4 win over Argentinians Sebastian Baez and Tomas Martin Etcheverry.

At the Adelaide International 1 tournament, there was a notable first-round win on Tuesday for Australian Thanasi Kokkinakis, who saw off compatriot John Millman 6-4 6-3.

Kokkinakis, a major talent as a youngster, is battling to reassert himself on tour after injury troubles, and beating Millman put his name up in lights for at least one day.

He reflected afterwards on the battle it has taken so far, with last year spent largely living out of a suitcase on the second-tier Challenger Tour.

"It was a gruelling year travelling," said Kokkinakis. "I've played a couple of times [in Adelaide] but just in exhibitions, so to play a real meaningful tournament and beat such a quality opponent, a proven veteran like Johnny, means a lot. I played great, and the support was great, so I'm really happy."

Cristian Garin prevailed in his hometown, crowned Chile Open champion with a three-set victory over Facundo Bagnis.

Garin, who had not won a match in 2021 before arriving in Santiago, claimed his first ATP Tour trophy on home soil thanks to Sunday's 6-4 6-7 (3-7) 7-5 triumph.

The top seed and 24-year-old only dropped one set throughout the ATP 250 tournament as he became the first Chilean player to win a home event since Fernando Gonzalez in 2009.

Bagnis was contesting his first final aged 31 and he was unable to see it through against Garin, who celebrated his fifth ATP title – all of them on clay.

Cristian Garin continued his quest for Chile Open glory as another upset in the other half of the draw paired two Argentinians in the semi-finals.

Top seed Garin is aiming to win an ATP Tour event on home soil for the first time in Santiago.

The 24-year-old was made to work by Peruvian qualifier Juan Pablo Varillas in the last eight on Friday, but he prevailed 6-4 6-4.

Garin was broken first in either set yet responded instantly on each occasion.

"I would love to be able to do something important in this tournament," the Chilean said. "It is special and I hope I can continue to win.

"I am playing better, in a semi-final and I am excited to do better, but I prefer to go step by step, game by game."

Daniel Elahi Galan is up next, while the highest remaining seed besides Garin is Argentina's Federico Delbonis, the number eight.

That is because Facundo Bagnis set up a meeting with his compatriot by defeating fourth seed Laslo Djere.

Bagnis, who had already claimed the scalp of fifth seed Frances Tiafoe, dropped the first set but recovered to advance 4-6 6-3 6-3 at the ATP 250 tournament.