Over the course of his 22-year career, Tom Brady has broken a lot of NFL records, including the all-time pass completions mark he set on Sunday against the Bills, but there is one record that he's still chasing and if he ends up breaking it, it will definitely be notable and that's because it's a record that Hall of Famer Peyton Manning considered unbreakable when he retired from football following the 2015 season.

The record we're talking about is the most touchdowns by a quarterback-receiver duo in NFL history. The record is currently held by Manning and Marvin Harrison, who connected for 114 touchdowns during their time together in Indianapolis. That total includes 112 scores in the regular season and two touchdowns in the postseason. 

When Manning held his retirement press conference in March 2016, he was asked if he thought any of his records would stand the test of time and his record with Harrison was the only one he felt might be unbreakable. 

"I think many records will be broken -- most of my records will be broken -- I don't believe that record that me and Marvin have of throwing the most touchdowns together will ever be broken," Manning said at the time

After breaking dozens of records in his career, Brady is now within striking distance of breaking Manning's unbreakable record and if he pulls it off, he'll be doing it with none other than Rob Gronkowski

With two touchdown passes to Gronk in Week 13, the Buccaneers teammates have now combined for a total of 104 touchdowns (90 in the regular season and 14 in the postseason). Although Brady and Gronk might not break the regular-season mark, they definitely could pass Manning and Harrison's overall total of 114. 

To break the overall record, Brady and Gronk would just need to combine for 11 more touchdowns. Although that might seem like a lot, it might happen more quickly than you think and that's because Gronk has been a scoring machine this year. The Buccaneers tight end has scored six touchdowns in just seven games. At that pace, it wouldn't be surprising to see Gronk score four more touchdowns over Tampa Bay's final five games. 

If that happens, Brady's total TD count with Gronk would reach 108. After that, they'd also have the playoffs to add to their total. Gronk is averaging 0.7 receiving touchdowns in his playoff career, so it wouldn't be surprising to see him tack on at least one more in the playoffs. Between the regular season and playoffs, if Gronk and Brady combine for just five more total touchdowns this year, that would put them at 109 and they would need just six more to break the record. 

At that point, Gronk and Brady would seemed destined to break the record in 2022, but only if both of them return to the field next season. On Brady's end, it seems like a done deal. Brady has a contract that runs through the 2022 season and he's made it pretty clear that he wants to play out the deal. If he wins another Super Bowl, maybe he'll lean toward retirement, but probably not, since returning to the field would give him a chance to do something that no player in NFL history has ever done and that's leading a team to three straight Super Bowl wins. 

As for Gronk, his brother said back in September that the tight end will probably play as long as Brady does, so if Brady is coming back next season, then you can probably assume that Gronk will also be back. 

If both guys return, it's almost a given that Brady and Gronk will break the hallowed record held by Manning and Harrison. It won't be as easy to break the regular-season record, but it could happen. Brady and Gronk currently need 22 touchdowns to pull that off and although that's a challenging number to hit, they would have 22 games to do it if both players return next season (five games this year and 17 next year), so Gronk would just need to average one touchdown per game, which is basically what he's doing this year.

Not to mention, if Brady and Gronk play until 2023, then it's a pretty much a lock that they'll break the record that Manning once thought was unbreakable.