Knapp was Rincon's first pitching coach, when Rincon was a teenage Minor Leaguer with the Twins, for whom he spent all but a half-season of his eight-year Major League career. As Minnesota's Minor League pitching coordinator, Knapp saw Rincon make his big league debut at the age of 22 in 2001, then pick up power and pick up the Twins in a big way two years later as part of baseball's most dominant bullpen alongside closer Joe Nathan, J.C. Romero and Jesse Crain.
From 2003-06, Rincon put together four straight seasons with at least 74 1/3 innings. He pitched in at least 75 games in three straight seasons starting in 2004, when he posted an amazing 11-6 record with a 2.63 ERA, 52 hits allowed and 106 strikeouts over 82 innings. He made 75 appearances in '05 despite a 10-day suspension for testing positive for performance-enhancing substances, then reached the same total the next year. He pitched in eight out of a possible 11 postseason games.
Rincon never became the closer thanks to Nathan's year-in, year-out dominance, but Knapp saw that kind of stuff when he was at his best.
"I think there's a lot of guys who thought he could finish games given the chance," Knapp said. "He had a fastball that had low ride to it, that looks like it's going to go in the dirt and comes back up, and a devastating slider."
Not until 2007 did the workload seemingly start to take its toll. Rincon still pitched in 63 games and threw 59 2/3 innings, but his 5.13 ERA on the year was more than two full runs above the previous season. His nine home runs allowed that year matched his total for his previous three seasons combined, and his strikeout total dropped.
While Rincon's fastball dropped, his mechanics seemed to slip. As Knapp put it, "I think that he just got a little jumpy in his delivery and his mechanics."
Once Rincon got off to a rough start in 2008, the Twins tried to designate him for assignment in mid-June in order to send him to the Minor Leagues to work out his troubles. He exercised the right to refuse the move, became a free agent, and a week later signed a Minor League deal on the other side of the division, with Cleveland.
He was back in the big leagues by the All-Star break, but he couldn't shake the struggles with his command. He finished the season with a 3-3 record and 5.86 ERA between the two clubs, surrendering 67 hits over 55 1/3 innings with eight home runs, 24 walks and 39 strikeouts.
Rincon went into his offseason program and felt well enough to pitch winter ball for the Cardenales de Lara in his native Venezuela. He gave up five earned runs on 10 hits over 5 1/3 innings, but four of those runs and seven hits came in a two-inning performance on Dec. 23.
In terms of his stuff, the Tigers have received encouraging reports. And when the Tigers headed out of the holidays with plenty of free-agent relievers on the market and spots to fill, they decided to take a shot.
There are still spots to fill, with just two jobs set and a little more than three weeks left before Spring Training. Fernando Rodney will be there in some form, whether at setup or closer, and Bobby Seay is set as a left-handed specialist. Detroit has pursued potential closers for much of the offseason with no signings, while they've also looked into adding another lefty.
Rincon likely won't close, but his presence in middle relief could be big. Knapp sees reasons for encouragement, from Rincon's recent stuff to the comfort level of being around so many fellow Venezuelan players.
"I think he can kind of split a gap, basically," Knapp said. "You win a lot of games because of the guys that are in the middle. Those are the most valuable guys on the staff, and the least rewarded. And that's what he did."
If he can do it again, it would be a big reward for the Tigers.