Mullens is expected to start Thursday's game against the Raiders, Adam Schefter of ESPN reports.
The 49ers' typical starting quarterback C.J. Beathard is still having difficulty gripping a football, paving the way for Mullens to see his first NFL action. Beathard will serve as Mullens' backup, though, after third-stringer Tom Savage was released Thursday afternoon. During the 2018 preseason, Mullens completed 31 of 43 passes for 396 yards, one touchdown and three interceptions.