Who is he?
Santana signed with the Los Angeles Angels as an amateur free agent back in 2000, though 2001 was his first professional season. He debuted in 2005 as a 22 year old, putting up a 4.65 ERA, 4.43 FIP, and 2.11 strikeout-to-walk ratio in 133 2/3 innings. Since then, his numbers have been all over the map. He put up a 5.76 ERA in 2007 followed by a 3.49 ERA in 2008 -- his only All-Star appearance -- then a 5.03 ERA in 2009. He was traded to the Royals before the 2013 season.
Why should we care?
When he feels like it, Santana can be an excellent middle-of-the-rotation pitcher. He was a solid #2 starter for the Royals in 2013, posting a 3.24 ERA in 211 innings. He outperformed his FIP and xFIP by a fair margin, but posted his highest strikeout-to-walk ratio since 2008 and cut his homer rate to a respectable (for him) 1.11 per nine innings.
Speaking of the homers, the dinger troubles I will mention below are his only real blemish, which turns into a positive in sort of a weird way. Let me explain: in his down seasons, he has still maintained decent walk rates and batted ball ratios. For example, Santana had a 5.16 ERA in 2012 because he allowed a ton of home runs. However, his xFIP (which controls for home run rate) was over a half run lower at 4.48 and his WHIP was only 1.27. He will give up his fair share of home runs because he's such an extreme fly ball pitcher -- his career rate is 40.7% -- but can be a good pitcher as long as he's not giving up an excessive amount of big flies.
Why should we stay away?
Hear that sound? That horrible screeching is the draft pick anchor attached to Santana's future contract. Since Santana declined a qualifying offer from the Royals, any team that signs him is required to forfeit their first round* draft pick. It's one thing to offer a long-term contract to a pitcher with stats as volatile as Santana's, but forfeiting a first round pick for that same player is another matter.
Dipping into those volatile stats, Santana is an extreme fly ball pitcher who gives up a ton of home runs. He has allowed at least 17 home runs in each of his nine big league seasons, topping out at a whopping 39 (!) in 2012. For comparison's sake, Doug Fister has never allowed more than 15 dingers in one year.
*The top 10 picks of the draft are protected, but the Tigers don't fall into this category so I don't feel like explaining it.
Will he end up in Detroit?
At this point, I have no clue. This isn't exasperation on my part, just confusion. There is a good chance that these Santana rumors are overblown at best and complete bunk at worst, but the idea of securing a starter now makes sense. If a trade opportunity for Max Scherzer unfolds, fire away. If not, move Drew Smyly back to the bullpen for another year. Do I agree with this? Not really, especially given the questions we have about Santana and the draft pick attached to him. But it could happen.