New England Patriots quarterback Tom Brady passes during the second half of an NFL football game against the New York Jets, Sunday, Dec. 31, 2017, in Foxborough, Mass. (AP Photo/Steven Senne)

Saturday night, when the New England Patriots host the Tennessee Titans in an AFC Divisional Round game, Tom Brady will start the 35th playoff game of his career. It is possible none have come with the distinct strain of uneasiness currently surrounding him. Brady finds himself at a peculiar stage, still excellent and yet ancient by the standards of his profession, exalted and yet constantly prodded for weakness. His age makes him a marvel, but also a target for dissection. The end will come at some point, and everybody is eager to spot it.

How could there be shakiness found in Brady, the reigning Super Bowl MVP, the heavy favorite to be named MVP of this season, the lodestone of a dynasty creeping toward the completion of its second decade? His team went 13-3, claimed the AFC’s top seed and scored the second-most points in the NFL, even as his favorite target, Julian Edelman, missed the entire season with a torn knee ligament.

Still, doubts have begun to bubble. Brady’s uncharacteristic unevenness down the stretch, coupled with the revelation tucked in an ESPN blockbuster on tensions within the Patriots that his own coaches have seen “slippage” in Brady this season, has prompted the latest round of questions about whether age has finally started to leech Brady’s brilliance.

If Brady was not 40, his 81.6 passer rating over the final five games of the season, which he played with a nagging Achilles injury, would be dismissed as part of a season’s typical ebb. The sterling late-season performance of Jimmy Garoppolo, the heralded backup the Patriots shipped to San Francisco for a second-round pick, would not have evoked panicked regret across New England.

In the ESPN story, an anonymous Patriots staffer described a play in which Brady overlooked an open receiver downfield for a possible touchdown, instead throwing over the middle to wideout Chris Hogan, who was tackled short of a first down and injured his shoulder. “Tom was trying to get it out quick,” the staffer told ESPN. “As fragility has increased, nervousness has also increased.”

Despite the emerging concern, experts see reason to relax. Kurt Warner, who played until age 38 and now analyzes the NFL for Westwood One, said he has seen no discernible drop-off from Brady this season overall, despite a late-season rough patch.

“I will say, I can’t remember too many five-game stretches where Tom kind of played at this level, or not up to his normal standard,” Warner said. “I’m just one that’s very leery of always [saying], ‘He hit the 40 wall.’ Or, ‘Father Time caught up to him between Week 10 and Week 12.’ That kind of stuff, I think it’s crazy. But people always want to do that. They’re looking for that moment, where everything starts to go the other direction.”

Zac Robinson, briefly an NFL backup quarterback and now an analyst for Pro Football Focus, watched and graded every snap every quarterback took in the NFL this season. He concluded Brady had the best season. He saw two games — a Week 13 loss at Miami and a Week 16 victory against Buffalo — when Brady’s level dipped, the first owing a poor overall performance from the entire Patriots offense, and the second pockmarked with unusual inaccuracy from Brady.

“Other than that, I don’t not see any diminishing accuracy, arm strength, movement in the pocket — any of that stuff,” Robinson said. “In terms of skittishness, he’s still the most poised guy and the best guy in terms of working the pocket.”

For aging quarterbacks, Robinson said, a telltale sign of age eroding skill is when a quarterback’s leg strength slips, leading to poor mechanics and decreased zip on passes. “I certainly don’t see that” from Brady, Robinson said. “He still has a ton of power in his arm and strength-wise, looks as good as it did, and you could argue it’s even better now. He’s still as efficient as ever with his mechanics, and it leads to him being able to keep that arm strength at the level it’s at.”

Warner believes he became a better quarterback as he aged, much for the same reason Brady has maintained elite performance. Both men relied not on physical dominance, but intellect and accuracy. Brady keeps a famously strict and intense physical maintenance regimen, but his mind has always been his primary weapon. Warner said as long as he kept a baseline of fitness, age never bothered him physically – he believes he would have the physical capability to make throws in an NFL game today, at 46.

“But if you suffer an injury, now that’s a whole different deal,” Warner said. “Especially if it’s a nagging injury where you got to fight through. That wears on anybody mentally, especially as you get older.”

Before Week 12, Brady appeared on the Patriots injury report with an Achilles issue. The injury coincided with Brady’s relative downturn, particularly against pressure and throwing deep passes. A statistical breakdown shows Brady passed deep with less frequency as the season wore on, but still at a higher rate than average.

In the season’s first seven games, Brady threw deep more often any quarterback in the league, and more often, by far, than at any point in his career, according to data complied by Pro Football Focus. Brady threw a pass at least 20 yards in the air – the barrier PFF uses for deep passing – 40 times, 15.3 percent of his throws, and completed 18.

In the first 11 games of the season, according to NFL research, Brady had a 113.5 rating on deep passes. In his last five games, Brady completed only 9 of 26 deep passes, with three interceptions and no touchdowns, good for a 25.3 rating.

Any study of Brady quickly reveals the importance of tight end Rob Gronkowski. In that final five-game stretch, Brady completed 5 of 6 deep passes to Gronkowski, but just 4 of 20 to all other receivers. Gronkowski’s best pattern, the seam route deep down the middle, meshes with Brady’s best throw. Robinson said Brady throws the seam pattern better than any quarterback in football, and Gronkowski’s size gives Brady options to squeeze the pass in against any coverage.

With Gronkowski suspended for Week 14 in Miami, Brady played his worst game of the season and one of the worst games of his career. He completed 6 of 17 passes when blitzed, Robinson said, as receivers failed to shake man-to-man coverage. “There wasn’t any quick outlets to get the ball out of his hand,” Robinson said. The Dolphins’ defense also forced Brady to make deep sideline passes, perhaps the weakest part of his game.

Brady did not appear on the Patriots’ injury report Tuesday, a first since his Achilles injury surfaced. For the nitpicking that can justifiably be done about Brady’s performance with the injury, the Patriots went 4-1 in those five games, including a victory at Pittsburgh in which Brady was sublime, particularly on a final drive heavily featuring Gronkowski.

“Watch him at the end of that Pittsburgh game,” Warner said. “Didn’t look like any age to me.”