Hector Santiago is important to the Twins, but what should they expect?

In a relatively quiet transaction heading into the weekend, the Twins made a pretty significant pitching decision.

Hector Santiago, acquired in a mid-year trade for Ricky Nolasco, settled with the team on a one-year, $8 million deal for 2017. He pitched poorly immediately after the trade and had a 5.58 ERA with the Twins, though his final seven starts (3-2 with a 3.19 ERA) were much better.

At that price and at age 29, the left-handed Santiago figures to be a good candidate to make the Twins' starting rotation in 2017. If the group of five includes Ervin Santana, Phil Hughes, Kyle Gibson, Santiago and a younger pitcher like Tyler Duffey or Jose Berrios, there are question marks galore.

Can Santana, 34, stay productive? Can Hughes and Gibson bounce back from disappointing 2016 seasons? Can a young pitcher step up.

For Santiago — who has been relatively consistent over the past four years and has an ERA under 4 in more than 600 innings as a starter — the question is a little different.

Local cat enthusiast/Baseball Prospectus editor in chief Aaron Gleeman, who is good at making the numbers DANCE for him, notes that Santiago has outperformed projections in recent years — leading him to believe Santiago's stats from 2013-2016 are "smoke and mirrors" that will cause an inevitable tumble at some point. Baseball Prospectus projects Santiago will have a 5.07 ERA this season.

Projections, though, are built on large data sets that focus on how a pitcher who pitches like Hector Santiago should fare. That leads to "outliers," or in plain speak "times when predictions fail."

In this case, the projections probably work against Santiago because he is terrible at preventing walks and home runs. He led the AL in walks allowed in 2016 (79) and home runs allowed in 2015 (29). That's a bad combination, and it's the main reason his FIP (fielding independent pitching, a measure of a pitcher if you take defense out of the equation) is almost a full run higher than his career ERA (4.73 vs. 3.84).

But that career ERA is very decent (better than the MLB average for the same span). He's flirted with danger but escaped because he can get strikeouts (8 of them per 9 innings in his career) and his clutch stats are quite good (batters have just a .604 career OPS vs. Santiago with runners in scoring position, compared to .763 with nobody on base).

So should the Twins expect Santiago to produce as he has produced (an ERA just short of 4) or should they expect Santiago to produce as he is projected to produce (with an ERA closer to 5)?

It probably depends on what you think of performance in the clutch. If you believe some pitchers have a knack for getting into trouble but also working their way out of it, you believe in Santiago. If you think "clutch" has a lot to do with luck and that Santiago is bound to pay for his combination of walks and homers, you don't believe in Santiago.

The Twins are clearly banking on the former. Given limited options for upgrading the rotation, new bosses Derek Falvey and Thad Levine are making an $8 million investment in Santiago's body of work. If they're right and Santiago continues to outpace projections, it will look smart. If they're wrong, he'll be overpaid and ineffective.

The margin of right or wrong here probably isn't the difference between making or missing the postseason for the 2017 Twins. But in a rotation filled with question marks, the number of pitchers who turn in best-case seasons will have a major impact on how the Twins fare. And Santiago might be the most interesting of the bunch.