It's a gamble, but definitely one worth taking. Wells will have much more value in spring training when a team inevitably loses a key starter to injury or realizes the staff they have isn't very good. The gamble, of course, is that Wells could get hurt himself thus making his value nothing. At that point though I think the Red Sox would be perfectly happy to hang onto Wells (not paying him his bonuses per start) as an insurance policy for later in the season.
However, we still have the "problem" of having one too many starters, so I think either Wells or Clement will get dealt by April 3rd.