He did this season.
Alex Smith has completed 61.0% of his passes over his career, 3.9% for touchdowns, 2.3% for interceptions, with an average yards per attempt of 6.7. He's been sacked on 8.2% of his dropbacks.
Ryan Tannehill has completed 61.9% of his passes, 3.9% for touchdowns, 2.4% for interceptions, with an average yards per attempt of 6.9. He's been sacked on 7.6% of dropbacks.
This season, Ryan Tannehill completed 61.9% of his passes, 4.1% for touchdowns, 2.0% for interceptions, with an average yards per attempt of 7.2. He was sacked on 7.1% of dropbacks. His team finished 6-10.
This season, Alex Smith completed 65.% of his passes, 4.3% for touchdowns, 1.5% for interceptions, with an average yards per attempt of 7.4. He was sacked on 8.7% of dropbacks. His team finished 11-5 and just won a playoff game 30-0.
This was easily the best statistical season of Alex Smith's career, unless you count the 9 games he started in 2012, when he completed a ridiculous 70.2% of his passes, 6.0% for touchdowns, 2.3% for interceptions, and 8.0 yards per attempt. He was sacked on 9.9% of dropbacks and had a record of 6-2-1 as a starter.
The year the 49ers went 13-3 and went to the NFC Championship game, he had a really low interception rate (1.1%) but was otherwise unremarkable.
Coaching matters.