Who to Start, Who to Sit in 49ers Week 1 Matchup against the Lions

Jimmy Garoppolo gets the start Week 1, leaving fantasy managers curious to see if Trey Lance also sees the field. Lance is eventually going to be a top-10 fantasy QB when he takes over, but for now it's a waiting game. Jimmy G enters healthy and faces a Detroit team that allowed the most fantasy points to quarterbacks and ranked last in pass defense DVOA last season. He'll also finally have a full group of weapons available Sunday after so many 49ers suffered injuries last year.

Raheem Mostert enters atop San Francisco's depth chart and has racked up 1,500+ yards from scrimmage with 16 touchdowns over his last 17 games (playoffs included). He remains a durability concern but would be the NFL's all-time leader in YPC (5.6) if he qualified (Jamaal Charles is the leader at 5.4). Even if he's not a workhorse like some other backs, Mostert can be considered a top-12 fantasy RB in Week 1 against a Lions defense that was gashed for an NFL-high 27 rushing scores and the most fantasy points by running backs last season. Even in an uncertain immediate role, Trey Sermon is a strong Week 1 flex option given the matchup. His season-long fantasy upside is also through the roof. Fantasy managers using either SF backs just have to hope Lance doesn't enter for goal-line packages to steal touchdowns.

Brandon Aiyuk looks ready to emerge as one of the game's elite receivers in Year 2 and is a weekly top-15 fantasy WR, while Deebo Samuel enters with serious health questions but is a strong fantasy start when on the field. Samuel somehow recorded more yards after the catch than receiving yards last season and will continue to be used in a variety of ways in San Francisco's offense. Trent Sherfield has emerged as the 49ers WR3 who would suddenly be worth adding in fantasy leagues should injuries strike.

George Kittle is a weekly top-three fantasy tight end when healthy and is also good news for San Francisco's running backs, as the team has averaged a full 1.0 YPC more over the last two seasons with Kittle on the field compared to off. Kittle should have his way against a Detroit secondary that was shredded for a league-high 8.5 YPA and 38 passing scores last season.

The 49ers defense looks absolutely loaded up front with Nick Bosa and Dee Ford returning, and Detroit's left tackle Taylor Decker missing practice this week. Rookie Penei Sewell struggled mightily in the preseason and may make his NFL debut Sunday as the team's left tackle. San Francisco's defense somehow finished No. 6 in DVOA last season despite a comical number of injuries, and they have a strong argument to be the top fantasy D/ST in Week 1.

Jared Goff and all Lions wide receivers are easy sits in fantasy leagues this week, while T.J. Hockenson needs to be started even in a tough matchup (the 49ers allowed the fewest fantasy points to tight ends last year) while projected to see so many targets. D'Andre Swift is also a must-start in fantasy leagues despite facing a strong San Francisco defense, as he's a special talent who'll rack up PPR points when on the field and reportedly has no limitations for Week 1.


Dalton Del Don has been with Yahoo Sports since 2013, covering fantasy football, baseball and basketball. He appears on multiple podcasts each week and currently resides in the Bay Area, where he is an avid fan of the Golden State Warriors and 49ers.

For Del Don's Week 1 Fantasy Preview and other fantasy insight from around the league, visit here.