All it took was one big fourth quarter from J.J. McCarthy to take over as the New York Giants’ starting quarterback. After the 23-year-old nearly led the team back from a 24-point deficit in its Week 6 loss, head coach John Harbaugh decided he’d seen enough of Jameis Winston and handed the job to McCarthy.

The young quarterback made the most of his first start, completing 71.4% of his passes for 252 yards and leading the Giants to a 27-21 overtime win over the Houston Texans in Week 7. Now, after New York’s Week 8 bye, McCarthy faces a much bigger test against the rival Philadelphia Eagles.

Not everyone is convinced he’s ready for it, though. Eagles legend Donovan McNabb has some serious reservations about the young QB.

Donovan McNabb Casts Doubt on J.J. McCarthy

The Eagles’ defense ranks No. 23 in the league with a PFN Defense Impact Score of 69.1 and 21st in points allowed at 25.3 per game. McCarthy could find some opportunities against that unit, but McNabb isn’t sold on the quarterback just yet.

During Monday’s edition of FanDuel’s “Up & Adams Show,” host Kay Adams asked McNabb whether he believes McCarthy is “the real deal.” The former Eagles QB shook his head and explained why he still has reservations about the Giants’ young starter.

“Where he was drafted (10th overall), I thought it was a stretch,” McNabb began. “It’s the same stretch that the Giants went with Daniel Jones in drafting him so high (6th overall).”

McNabb then pointed to McCarthy’s time at Michigan, where he played in a system that didn’t ask him to do too much.

“[McCarthy] was in a system, kind of a West Coast system, where he was asked to manage the game at Michigan. He had a great running game, utilized the quick game, intermediate game, and then the thing that kinda boosted him is his mobility. His ability to get outside the pocket and scramble when needed. He’s not Lamar Jackson, but he’s serviceable to be able to get outside the pocket,” added the former QB.

So, what’s behind the quarterback’s early success in New York? McNabb believes the answer lies in how closely John Harbaugh’s offense resembles the system McCarthy played in at Michigan.

“What you’re seeing is the type of offense that he ran under Jim Harbaugh that John has incorporated into what he’s doing with the Giants,” McNabb explained. “It’s a run-the-football, downhill in the mid zone, mid and inside zone. It’s the quick game, and you’re running some boots and nakeds to get him outside the pocket. Now he looks efficient when he’s connecting on slants or hitches or maybe quick outs or curls, and occasionally might get a deep ball up the middle versus Cover 2 or something like that.”

If the Eagles want to slow McCarthy down, McNabb believes defensive coordinator Vic Fangio needs to make him uncomfortable. That means stopping the run and bringing pressure to force the young quarterback to make plays from the pocket.

“There are plays where he’s rolling,” McNabb admitted. “But until you start to blitz him and stop the run. When you stop the run and start blitzing him, now you force the ball to be in his hands for decisions to be made. That’s when you’ll see the J.J. McCarthy that we’ve seen throughout his first couple of years in Minnesota.”

McCarthy has thrown passes in just two games for the Giants so far and has made only one start. The early returns have been encouraging, but it’s still a small sample size, and the inconsistencies that followed him in Minnesota could resurface in New York too.

So far, though, McCarthy has shown better touch on some of his throws, fitting passes over linebackers and in front of safeties. That’s something he struggled to do consistently with the Vikings.

McNabb believes the Eagles could expose those old issues by bringing more pressure and forcing McCarthy to make quick decisions.

At least, that’s the approach McNabb would like to see. Whether Fangio takes the same route on Sunday remains to be seen.