The 49ers had a surprise starter Sunday on defense, and the Miami Dolphins didn't wait long to expose him.
Ahkello Witherspoon is active, but his ailing hamstring didn't allow him to start. So coach Kyle Shanahan turned to Brian Allen, and the start of Week 5 couldn't have gone much worse for Allen and the 49ers. On the Dolphins' very first play of the day, Allen was burned by receiver Preston Williams for a 47-yard gain.
Allen also was called for a 15-yard penalty later on the Dolphins' first drive, which put them in the red zone. On Miami's second drive, he was beaten by Davante Parker for 28 yards. Both drives ended in a touchdown by the Dolphins.
It's safe to say Allen's first career start in the NFL didn't go as planned, and 49ers fans aren't happy.
On the Dolphins' fourth drive of the day, Allen gave up a 22-yard TD to Parker on 3rd-and-goal.
With 4:40 remaining in the second quarter, Witherspoon replaced Allen. The 49ers were down 21-7 at the time. Allen last played in an NFL game in 2018 when he suited up in six for the Pittsburgh Steelers.
The 49ers are down their top three cornerbacks as Richard Sherman still is on the injured reserve with a strained calf. Emmanuel Moseley was ruled out with a concussion.
With injuries derailing the 49ers' secondary, Allen and Jason Verrett started at cornerback against the Dolphins.