Washington had not won a play-off game since 2006 and had not finished the season with a winning record since 2016.
But rookie quarterback Jayden Daniels helped transform them into one of this season’s highest scorers, along with the Buccaneers.
The Commanders have made a habit of claiming late victories this season and it continued in Tampa Bay, where Daniels and Bucs quarterback Baker Mayfield threw two touchdown passes apiece.
The score was tied 10-10 at half-time, with Dyami Brown’s effort for Washington cancelled out by a Mike Evans score right before the half.
Gonzalez’s second field goal edged the Commanders back in front, before Bucky Irving’s touchdown helped the Bucs into a 17-13 lead.
The Bucs’ defence made a big stop to win back possession early in the fourth quarter but, on their next drive, a Mayfield fumble, recovered by Washington’s Bobby Wagner, allowed Washington to go 20-17 up through a Terry McLaurin touchdown.
Chase McLaughlin’s second field goal for Tampa Bay made it 20-20 with less than five minutes left, before the Commanders set up a 37-yard attempt for Gonzalez, which bounced through off a post.