Recently acquired Brad Penny will almost surely have a spot in the Tigers rotation if he is healthy. That's a big "if" as he has been suffering various health problems since 2008. His last good year was 2007 when he had an excellent 3.03 ERA in 33 starts for the Dodgers. He was terrible in 2008 posting a 6.27 ERA and missing the second half with a sore shoulder. He was almost as bad in 24 starts for the Red Sox in 2009. However, he had six solid starts down the stretch for the Giants.
He got off to a strong start last year with the Cardinals. On the advice of pitching coach Dave Duncan, he threw his fastball less often a bit and increased the use of his split finger pitch. The results were good - a 3.23 ERA, 9 walks in 9 starts and a 53% ground ball rate. His career seemed rejuvenated until he went on the disabled list with back and lat problems. His ailments didn't appear to be serious at the time, but he never returned to the mound.
So, the Tigers are hoping they get the Brad Penny that had 15 good starts for the Giants and Cardinals in late 2009/early 2010. If he only gives them a good half season, it will be a big help. At the very least, he gives them depth at the back of the rotation which previously included Phil Coke and Armando Galarraga.
Coke has virtually no major league experience as a starter and there is no guarantee he can make a successful transition from the bullpen. Galarraga has been a starter for three years, but Penny has a better track record. Specifically, Penny has better control and a lower home run rate. My guess is that Galarraga will start the season in long relief. Chances are they'll all get a good number of starts by the time the season is over. A team can never have too much pitching depth.