There are no real obvious replacements for either Denard Span and Ben Revere at the top of the Twins lineup. In addition to creating an opening in center field, trading those two created openings for both the leadoff and number two hitters. Here is a rundown of the Twins lineups with some comments on how various spots will be filled.
There are three basic skills teams look for in a leadoff hitter. One is to get on base. The second is to be able to advance themselves once they get on base by stealing or advancing an extra base. The third is to look at a lot of pitches so the hitters that follow see the pitchers stuff.
The most likely candidate here is Darin Mastroianni if he wins the center field spot. He is a better base stealer than Span, but he gets on base less often. I don't know about his pitch taking ability. If Aaron Hicks wins the center field spot he would bring some tools to the leadoff role also. He has speed and is reputed to be a patient hitter. But the Twins may not want to put that much pressure on him as a rookie. Joe Benson doesn't fit the leadoff spot very well at all. He is more an all or nothing power hitter who should be batting lower in the order. Jamey Carroll would also be a possibility. He gets on base, but lacks the speed to advance himself.
Teams are looking for a player with skills similar to the leadoff batter, but with the additional ability to advance runners. Carroll fits this role pretty well. He gets on base, he is a veteran and he doesn't strike out very often. Brian Dozier would be another possibility here if he can hit like he did in the minor leagues.
There have been some who have suggested that Joe Mauer should be moved up to the number two spot because he gets on base a lot. But Mauer's on base ability has as much value batting third. And, with him batting second, both he and whoever replaces him in the number three spot would see fewer base runners. To put that in perspective, even if the number two hitter only had a .300 OBP, Mauer and the new number three hitter would each see 48 fewer base runners in the first inning. Mauer may not hit many home runs, but he has enough pop that you want him at the plate with runners on base.
Teams usually put their best hitter in the number three spot. They are looking for a combination of the ability to drive in the runners ahead of them and getting on base for the runners behind them. Mauer is the Twins number three hitter and likely to stay there. If Morneau went back to hitting .300+ with home run power, that might change. But that isn't likely to happen in spring training.
Teams put their best power hitter in the cleanup spot. The idea is that they will see a lot of batters on base and use their power to drive them in. Until last year, Justin Morneau was the Twins cleanup hitter. The problem is that both he and Mauer are left handed and Morneau has some trouble with lefties. So last year, with Morneau's numbers down, the Twins moved Josh Willingham into this role. If Morneau returns to his MVP production he belongs here. But I suspect the year will start with Willingham in the cleanup spot.
This guy is usually the next best cleanup hitter. And that is how it will work with the Twins with either Willingham or Morneau batting fifth.
Ryan Doumit, as the next best hitter, will most likely bat sixth.
Chris Parmelee and Trevor Plouffe will probably trade this spot depending on the pitcher with Parmelee here the most against righties. The development of these two as offensive players could transform this lineup into one pitchers would rather skip.
Plouffe or Parmlee.
Pedro Florimon or whoever else wins the second infield spot. Florimon has some speed on the basepaths, but he doesn't hit enough to be much of an offensive force.
That lineup has the potential to make the Twins a contender. But there are enough question marks that it isn't likely they will all have positive answers.