Fantasy Football Week 17 Start ‘Em, Sit ‘Em: Brock Purdy vs. Baker Mayfield

Evaluating who to play in fantasy football in week 17 between Tampa Bay Buccaneers QB Baker Mayfield and San Francisco 49ers QB Brock Purdy.

Dec 22, 2025; Indianapolis, Indiana, USA; San Francisco 49ers quarterback Brock Purdy (13) warms up before the game against the Indianapolis Colts at Lucas Oil Stadium. | Trevor Ruszkowski-Imagn Images

Two QBs ranked close to each other in our week 17 fantasy football rankings are the San Francisco 49ers QB Brock Purdy and the Tampa Bay Buccaneers QB Baker Mayfield. Here is a breakdown of who to start and who to sit between the two in fantasy football this week.

Brock Purdy

Dec 14, 2025; Santa Clara, California, USA; San Francisco 49ers quarterback Brock Purdy (13) throws a pass during the fourth quarter against the Tennessee Titans at Levi's Stadium. | Cary Edmondson-Imagn Images

49ers QB Brock Purdy is coming off his best game of the season in week 16, and one of the best games any QB has had this season in the NFL. Against the Indianapolis Colts in a week 16 Monday night game, he went 25-34 passing for 295 yards and also threw for five TDs. This performance from Purdy equated to him being ranked as QB1 in fantasy football for the week. This extends a slight streak of Purdy throwing two consecutive games with three or more passing TDs. He will look to continue this streak in week 17 against the Chicago Bears.

The Bears this season are allowing the 18th fewest passing yards per game.  In their last three games, they have allowed the eighth fewest passing yards per game, as teams have averaged 184.7 passing yards per game against them. QBs during this three-game span have combined for a TD-to-INT ratio of four to four. The best fantasy performance in this stretch of games came from Green Bay Packers QB Jordan Love. He threw for 234 passing yards and three passing TDs in week 14. In fantasy football, he ranked as QB11 for the week against Chicago.

Baker Mayfield

Dec 21, 2025; Charlotte, North Carolina, USA; Tampa Bay Buccaneers quarterback Baker Mayfield (6) passes the ball in the third quarter at Bank of America Stadium. | Bob Donnan-Imagn Images

Baker Mayfield’s after a hot start to his 2025 fantasy football campaign, his production has now dropped off a cliff. Last week against the Carolina Panthers, he threw for 145 yards and one TD pass. This is his fifth game out of his last six, where he has thrown for under two TDs, and his fifth game out of his last six where he has thrown for under 200 passing yards. In the first six games of the season in fantasy football, Mayfield was QB4; in the last six games he has played, as shown above, Mayfield ranks as QB18. He will try to break this streak of poor play in week 17 against the Miami Dolphins.

The Dolphins this season are allowing the 14th fewest passing yards per game. In their last three contests, they are giving up the 17th fewest, allowing 215 passing yards per game. QBs in these games have combined for a TD-to-INT ratio of six to two. In their latest game against the Cincinnati Bengals, they gave up a mammoth game to QB Joe Burrow. He threw for 309 yards and four TDs, making him QB5 for the week in fantasy football. 

Final Verdict

When it comes to who to start and who to sit in fantasy football between Purdy and Mayfield in week 17, Mayfield should sit, and Purdy should start. Both QBs have similar levels of opponent, making the main separator Purdy’s recent play compared to Mayfield’s.

In his last six games, Mayfield has struggled in fantasy; three of his opponents have allowed more passing yards than his week 17 opponent, the Bears. With this, it feels too big a stretch to start Mayfield this week over Purdy, who is in the midst of a heater in fantasy football.