Why is Tom Brady having such an off year?

Julian Edelman (11) has been one of Tom Brady’s few familiar targets in the passing game.jonathan wiggs/globe staff/Globe Staff

FOXBOROUGH — The Patriots’ struggles aren’t all Tom Brady’s fault. They aren’t all the fault of the receivers. They aren’t all the fault of the offensive line or coaching staff.

But though he’s seemingly loath to admit anything is wrong with him, saying on Wednesday, “I feel really good” when asked about his mechanics, statistically Brady is having a very un-Brady-like season.

He’s on pace for career lows — or career highs — in a few statistical categories, and is putting up numbers typically seen from mediocre quarterbacks rather than a future Hall of Famer.

There have been extenuating circumstances, of course. Wes Welker and Aaron Hernandez are gone, Rob Gronkowski returned to the lineup only last week, and Brady has had to work overtime to integrate three rookie receivers into the offense.

There’s no way to know how much those are factoring into Brady’s play. What we’re seeing is likely a combination of an off year by Brady and all of the changes.

“I think over the course of the season you go through the things that you think you need to do better and things that you are doing well, how you can build on those things,” Brady said. “You evaluate those on a weekly basis because one week does not always lead to the next week in the NFL, so you have to get right back in the tank. You get out there on the practice field and work on the things you need to work on.

“As a team, ultimately we are trying to score points, and what my job is, is to find open guys and give them a good ball and try to get them in the end zone.”

A 63.7 percent passer for his career entering this season, Brady is completing just 55.4 percent of his attempts in 2013, which is 29th in the league. His career low is 60.2 percent in 2003.

Brady did not complete 50 percent of his passes in losses to the Bengals and Jets, and for the first time in his career has three sub-50 percent games in a season. He had two each in 2003, ’06, and ’09, and none from 2010-12.

One area in which Brady usually shines is yards per attempt, an often overlooked but generally important statistic. This year, his YPA is 6.0, again on pace to be the lowest of his career (6.3, 2002). Brady’s career mark of 7.5 YPA is tied for eighth among active quarterbacks, and is likely reflective of the short passes and screens the Patriots have favored throughout his career.

The Patriots were 2 for 2 in the red zone against the Jets last Sunday, a positive sign for an offense that has struggled to score from inside the 20 (they’ve now scored touchdowns on 11 of 24 opportunities, creeping up to 26th in the NFL), but both of those were rushing touchdowns.

Brady has eight touchdown passes, on pace for 18 for the season, which would tie his career low from 2001, the year he became the starter. Over the last three years, he had 36, 39, and 34 TD passes.

Quarterback rating is debated by those who like football metrics, but the formula the league uses has been in place for decades. Brady’s career rating entering this season, 96.6, is stellar, though ratings have gotten higher across the board as the passing game has opened up. Brady is off that mark by more than 20 points currently — he’s at 75.3, and that’s a full 10 points lower than the 85.7 he posted in 2002, his career low.

There’s also the question of the deep ball, and more curiously, how he’s throwing to the right third of the field.

According to ProFootballFocus.com, Brady has completed fewer than 25 percent of his attempts traveling 20-plus yards (9 for 37), with one touchdown and two of his five interceptions.

Undoubtedly, longer passes have a higher degree of difficulty, but over the last three seasons, Brady has completed a third of his deep balls (72 for 216), with 27 touchdowns and 11 interceptions. In 2010, when Brady had a remarkable four interceptions on the season, three were on deep passes.

This season, Brady’s numbers are also down throwing to the right side of the field. Again using stats from ProFootballFocus.com, Brady is completing just 45.8 percent of all passes to receivers on the right third of the field; to the middle and left, that number is 60.6 percent.

Last season, his completion mark to the right side of the field was 53.7 percent, and 69.5 percent to the middle and left. In 2011, it was 66.4 percent to the right side and 69.5 percent to the remainder of the field.

One possible factor: Brady already has been sacked 20 times, on pace for a career-high 46, far higher than the 27½ sacks per season over his first 11 seasons as the starter. His previous high is 41 in 2001.

Asked specifically about his mechanics and the work he did with his new personal coach, Tom House, Brady danced around the question.

“You’re just trying to work on getting the team into the end zone most of all,” he said. “You have to try to be a good football player and not think about or overdo things. When we do it well, it looks good and we get the ball in our end zone, and when we don’t there are definitely things we need to improve on, because our goal is to score points.

“When we don’t score as many points, then we’re not doing as good a job as we need to . . . Certainly I expect to go out there and play as best I can. That would be hugely important for the team.”

Does Brady feel his mechanics are good?

“Yeah, I feel really good,” he said.

Whenever the struggles of the offense, or, as on Wednesday, his own struggles are broached, Brady brings up the Patriots’ winning record.

That they are 5-2 can’t be denied. But just as it was unfair of the Patriots to ask Brady to pull so much of the weight over the last couple of years while the defense was rebuilt, it’s fair to expect that he and the offense do their part now, when the defense has shown improvement.

Balance is necessary.