The 49ers built their roster so well in recent years they survived monumental mistakes at the most critical position of all.

San Francisco drafted defensive lineman Solomon Thomas third overall in 2017 rather than taking Patrick Mahomes. The 49ers then traded three first-round picks four years later to move up to select quarterback Trey Lance third overall.

Thomas and Lance are no longer on the roster. Mahomes is a two-time MVP, two-time champion and San Francisco’s opponent in Super Bowl 58 at Allegiant Stadium on Sunday.

Those types of swings-and-misses on quarterback are often death knells for teams. Not so for the 49ers. They’ve reached four NFC title games and two Super Bowls the last five seasons despite those colossal whiffs.

It comes back to how well they’ve built around the quarterback position.

That allowed San Francisco to find a passer with the last pick of the 2022 draft in Brock Purdy and have him step in and produce. Purdy deserves credit for seizing his opportunity and having one of the best statistical seasons in the NFL this year. But he got a lot of help from the 49ers’ excellent supporting cast.

Almost 59 percent of San Francisco’s roster is homegrown. The team has been effective in early rounds, taking wide receiver Brandon Aiyuk in the first and wide receiver Deebo Samuel in the second. But the 49ers have been fantastic in the fifth round and beyond. They have reeled in 16 players through those rounds. That includes several standouts, like Purdy, tight end George Kittle and wide receiver Jauan Jennings.

San Francisco also bet big up front on defense. The team drafted linemen Arik Armstead, Nick Bosa and Javon Kinlaw in the first round. The 49ers have reached outside the building to create as much pass rush as possible, too. They added Chase Young at the deadline this season.

The club has several homegrown stars in the back seven as well. Linebackers Fred Warner and Dre Greenlaw were draft picks. So were cornerbacks Ambry Thomas and Deommodore Lenoir and safety Ji’Ayir Brown.

San Francisco has used free agency and the trade market to add talent on occasion. Some of the pieces the team brought in include offensive tackle Trent Williams, running back Christian McCaffrey and safeties Charvarius Ward and Tashaun Gipson.

But investing money that way is easier when the core is built through the draft. That’s what the 49ers have done, despite some strikeouts under center that would have set lesser clubs back.

Contact Vincent Bonsignore at vbonsignore@reviewjournal.com. Follow @VinnyBonsignore on X.