The daily roster move: Polanco down, Darnell up

Logan Darnell is 5-5,
3.43 in Triple A this year.

The Twins are in a period in which they are shuffling bodies around to cover for a rotation vacancy and because they're downshifting from veterans to prospects -- or at least unestablished players -- as it becomes obvious that contention remains an illusion. The upshot is that something marginal is happening every day.

Friday's move was the demotion of Jorge Polanco -- recalled for a day after Kendrys Morales was traded Thursday for a minor leaguer -- to bring up Logan Darnell, who will get the start Saturday in place of Kris Johnson, who was demoted after Monday's start to make room for Yohan Pino, who started Tuesday.

Meanwhile, the true prospect starters -- Alex Meyer and Trevor May -- remain in Rochester.

This is a growing irritant to a vocal block of Twins fans, who are wondering why we're getting a parade of minor league vets in Johnson and Pino and not seeing the guys who could actually matter down the road.

My guess is that the Twins are (a) wary of May's health after he missed almost a month with a calf injury and (b) unwilling to bring Meyer up with his (unofficial) innings limits. I think -- hope might be the more accurate verb -- that the idea is to bring May in to replace Kevin Correia in the next week or so after Correia is traded. (That, of course, is a scenario that assumes Correia will be traded, which may be merely wishful thinking.) I don't expect to see Meyer in Minnesota at all in 2014.

Darnell is sort of a medium ground between the Meyer-May duo and the Johnson-Pino pair: Not as high-ceiling as the former two, younger than the latter two. He's a lefty, and I suspect that his ultimate role, if any, with the Twins will be in the bullpen. Brian Duensing 2.0, perhaps.

As a starter, Darnell's not staying long. If Duensing is on the trade block -- and a contender may well be interested in him and his 2.27 ERA -- Darnell might stick around for a trial in the pen.

Bottom line: Just because Darnell is here today doesn't mean he'll be here tomorrow, and if he's here tomorrow it doesn't mean he's remaining in the rotation. The roster shuffling is far from over.