With Chris Carpenter already out for likely 2 months, the Cards had another starter potentially go down when former Red Kyle Lohse felt a "pop" in his knee area. He had an MRI yesterday and the results will be known today apparently.
Many will argue that Lohse was signed for too much money and years (4 years, $41M, in a down market where the Crads jumped the gun) but he has certainly been a durable pitcher in his career. I'd consider him similiar to Arroyo.