Pestano was excellent in 2011 and 2012, but he suffered an elbow injury shortly before the 2013 season began, and he's never been the same since then. He'd given up 8 hits while recording just 8 out so far this season, and was hit hard last night, nearly blowing (with some help from a Nick Swisher error) an 8-2 lead. His velocity is not what it used to be, and it's unclear whether that will rebound, and/or if he'll be able to turn into an effective pitcher with his current stuff.
Lee is a 26-year-old right-hander. If you're new around here, save your breath on the observation that his name is a combination of former Tribe aces CC Sabathia and Cliff Lee, as someone else beat you to it 4 or 5 years ago. Lee pitched 4.1 innings for the Indians last season, but has spent most of the last 3 seasons in Columbus ( though he missed most of 2012 due to Tommy John surgery), where he's put up a 2.39 ERA, with an impressive 11.8 K/9 against just 2.8 BB/9.
It remains to be seen whether Francona will stick with the 8-man bullpen once Michael Bourn and Jason Giambi have both returned from injuries (Bourn could be back this weekend, Giambi might be ready a week or two after that).