From the Strib:
Liriano, a lefthander, was called up to the majors by the Twins on Friday, bringing with him a fastball in the mid-90s and an arsenal similar to Johan Santana's...Liriano, 21, was 3-5 with a 3.64 ERA in 13 starts at Class AA New Britain. He had 26 walks and 92 strikeouts in 762/3 innings. That earned him a promotion to Class AAA Rochester.
At Rochester, Liriano was 9-2 with a 1.76 ERA in 14 starts, with 24 walks and 112 strikeouts in 91 innings. Combined, that's a 12-7 record, 2.63 ERA with 50 walks and 204 strikeouts in 1672/3 innings -- which is why he's considered one of the best pitching prospects in the game. In addition to his fastball, Liriano throws a slider and a changeup.
"[General Manager] Terry Ryan told me he was very good," manager Ron Gardenhire said. "Terry doesn't throw out 'very good' very often."