The Philadelphia Eagles visit the San Francisco 49ers searching for their first win of the 2020 season and with questions abounding about their franchise quarterback, Carson Wentz.

Philadelphia signed Wentz to a four-year, $128million extension prior to last season, a decision that looked on the way to being vindicated after he dragged an injury riddled Eagles team to the playoffs.

However, Wentz has endured a dismal start to the 2020 campaign, with his and head coach Doug Pederson's time in Philadelphia reaching a nadir in a 23-23 tie with the Cincinnati Bengals last Sunday.

Wentz is completing under 60 per cent of his passes, already has six interceptions and is averaging a career-low in yards per pass attempt (5.6).

His failings have been particularly prominent in the second half of games, with the Eagles unable to close out wins over two supposedly inferior opponents in the Bengals and, in Week 1, the Washington Football Team.

Using Stats Perform data, we examine Wentz's poor start, whether he is solely to blame and if things can be turned around this season.

SECOND-HALF STRUGGLES

From 2017 through to the end of the 2019 regular season, Wentz had a passer rating of 99.6 during the second half and overtime, putting him eighth among 44 qualifying quarterbacks.

His penchant for success after the half-time interval has not carried into 2020, however.

Wentz's passer rating in the second half/overtime this season is 42.8, bottom in the league by some distance, with the next worst - Baker Mayfield of the Cleveland Browns (66.3) - well ahead of him.

Four of his interceptions have also come after the first half while his yards per attempt figure in the second half/overtime of 4.57 is also the worst in the league.

The drop-off from Wentz's first-half passer rating of 86.9 to his second-half rating of 42.8 is the largest in the league at minus 44.1.

Those are astonishing numbers and would put him ninth on the list of biggest second-half drop-offs since 1932. Donovan McNabb is fourth on that list for his efforts for the Eagles in 2004, but his passer rating dipped from and to much higher levels (127.3 to 79.3).

In other words, when Wentz hits the field in the second half, he is enduring a dip in performance unlike any other experienced by a Philadelphia quarterback, and very few others in NFL history.

A TURNOVER-LADEN START

Wentz has been extremely careless with the football - his six interceptions are tied for fifth-most in Eagles history through the first three games while his seven turnovers in three games is second in franchise history behind Michael Vick in 2012 (9).

His propensity for turning the ball over has been compounded by an inability to push the ball beyond 10 yards with any consistent success.

On throws travelling 1-10 yards in the air, Wentz is still efficient, completing 74.5 per cent of his passes at an average of 6.56 yards per attempt.

However, he is completing just 33.3 per cent of his passes between 11-20 air yards at an average of 5.44 yards per attempt with two touchdowns and three interceptions - he only had nine picks on such throws in his entire career prior to this season.

Wentz's completion percentage on throws of 11-20 yards is the worst of his career, even coming in lower than his rookie year in 2016 (49.6), and there has also been a startling decline on third down.

Between 2017 and 2019, Wentz's third-down passer rating of 103.6 was second behind only Patrick Mahomes (114.8). In 2020, it is 64.8, though the downturn is not entirely his fault.

A LACK OF PROTECTION

Injuries to the offensive line have not helped Wentz. They lost Pro Bowl guard Brandon Brooks before the season to a torn Achilles while starting left tackle Andre Dillard was placed on injured reserve with a torn bicep.

Jason Peters, who the Eagles re-signed after Dillard's injury, is on IR with a toe injury and right tackle Lane Johnson is battling an ankle issue.

The protection issues have made life very difficult on Wentz, who has been sacked 11 times, with that number tied for third-most in the NFL, though eight came in Week 1.

Only four quarterbacks have received more than the 21 hits Wentz has taken in 2020, while the 49 QB pressures against him are tied-seventh in the league.

Wentz is getting very little help up front, and his cause would certainly be aided by having healthier pass-catchers.

ALSHON'S TELLING ABSENCE

Earlier this week the Eagles had just two healthy wide receivers, Greg Ward Jr. and John Hightower, on their active roster.

Philadelphia recently saw tight end Dallas Goedert suffer an ankle injury but arguably the most important absentee is wideout Alshon Jeffery.

Jeffery is sidelined with a foot problem, meaning the Eagles will be without a receiver who has caught 17 touchdowns from Wentz between 2017 and 2019.

In 10 games without Jeffery, Wentz averages 6.28 yards per attempt and has a touchdown to interception ratio of 1.44.

Those numbers increase to 7.33 YPA and 3.94 TD-INT in Wentz's 33 games with Jeffery. Additionally, he has connected 49 times with Jeffery on throws of 11-20 yards since 2017 for 762 yards and nine touchdowns.

He has also targeted Jeffery 95 times on third down in that same span, completing 51 of them for 560 yards and eight touchdowns.

A healthier offensive line and the return of Jeffery could go a long way to fixing Wentz's issues but, by the time the Eagles get those players back it could be too late.

San Francisco's defense, which has allowed opponents to reach the red zone just four times this season, should relish playing a turnover-prone quarterback struggling to throw beyond 10 yards.

If the banged-up Eagles cannot find a way to escape the Bay Area with a win, history is against them turning it around regardless of what Wentz does going forward.

Only two teams - the 1963 Buffalo Bills and the 1992 San Diego Chargers - have made the playoffs after going winless through four games. Wentz and the Eagles have shown little sign of having what it takes to join that select group.