Sources: Tigers close in on Brad Penny

The Detroit Tigers are the front-runners to sign free-agent righthander Brad Penny, sources told ESPN The Magazine's Buster Olney.

Penny is recovering from an upper back injury that limited him to just nine starts in 2009.

Penny was 3-4 with a 3.23 ERA after signing a one-year, $7.5 million contract with the St. Louis Cardinals in the offseason.