You’ll recall that when Matt Garza was sent down we researched his service time and found out that it would behoove the Twins to call him up very late in May to bump his free agency back a year, and until the all-star break to bump his arbitration back a year. Let's do the same with Kevin Slowey, Glen Perkins, and Scott Baker.
(By the way, if you want some of the specifics, click on that Garza link. It talks about how the service time is set up in more detail.)
Service Time coming into the year: 13 days
Free Agency Clock: The Twins called up Perkins about 10 days into the season. Ouch. That means if he stays on the roster all season he'll be eligible for free agency after 2012, whereas if they send him back down for about a week, he'll be eligible after 2013. That's not a bad reason to not want to rush him into the rotation.
Arbitation Clock: If he stays in the league for the whole year, he'll be eligible for arbitration after 2009. To bump it back to 2010, he would need to spend aproximately 11 weeks back in AAA.
Service Time coming into the year: 0 days
Free Agency Clock: Because Slowey didn't start the season with the Twins, he won't be eligible until 2013 whether he's called up now or called up at the end of September.
Arbitration Clock: If Slowey is called up now and sticks, he'll be eligible for arbitration after 2009. If he isn't called up until the end of June, he'll be eligible for arbitration after 2010.
Service Time coming into the year: 165 days
Free agency clock: If Slowey is called up any time prior to the middle of September, he'll be eligibile for free agency after the 2012 season, so there is no real impact.
Arbitration Clock: There also is no real impact on his arbitration clock if Baker is called up now. He's alreay missed the 30 days he likely needed to be a "Super 2", so if he's called up and stays, he'll be eligible for arbitration following the 2009 season. To bump it back a year, the Twins would need to wait until May of 2008.
As I mentioned already, there are also two good reasons to keep Garza down a bit longer. This shows there is a good reason to delay Slowey's debut by another month, and a good reason to keep Perkins in the bullpen and send him back down when they face interleague play in a month.
But Baker is a different story. His critical time is over for both clocks. It'll be interesting to see if the Twins deem him the "most ready".