With a pair of open roster spots -- and with safety Budda Baker needing an MRI on his knee after Sunday's game -- the Cardinals signed a pair of cornerbacks Wednesday, including former second-round pick David Amerson.

The Cardinals also signed cornerback Leonard Johnson, who has been on five teams since 2012, and added offensive lineman Rick Leonard to the practice squad. Leonard was a fourth-round pick of the Saints in the most recent draft and spent time on the practice squads of the Saints and Rams.

Amerson was with the Chiefs in preseason before being released. He was drafted by Washington in 2013, and spent the past three seasons with the Raiders -- who visit State Farm Stadium Sunday. He has eight career interceptions.

Johnson is a one-time undrafted free agent who has spent time with the Buccaneers, Patriots, Panthers, Bills and Giants. He has five career interceptions, and started seven games for Buffalo last season. He was released by the Giants at the end of preseason this season.

Both Baker and fellow safety Rudy Ford were sitting out during the open portion of Wednesday's practice.

If Baker is sidelined for any games, the Cardinals have been moving starting cornerback Bené Benwikere to Baker's slot/safety spot, and using Jamar Taylor opposite Patrick Peterson at cornerback.