I like it because if he can return to form in time for the postseason, that does nothing but help us offensively.
I don't like it for two reasons: one, Ruiz has done pretty well at 3B so far (other than his air-mailed throw in the 9th against Duke on Sunday), and I'm not sure I want him out of the lineup--especially if his bat picks back up. Two, I would be OK with letting this type of injury/surgery fully heal from now until next season, and not risking Thompson hurting himself for next season or longer.
The other conundrum this presents to Morris is who to take off the field. Do you bring Kennedy back in at C, move Collins to 1B, and put Thompson back at 3B (which weakens your D on the corners, but sits Fieger and puts Thompson back in)? Do you keep a struggling Fieger at 1B or 3B for defense, and put Thompson at the other spot (which helps offensively but hurts defensively by flipping Thompson for Ruiz)? Personally, I would DH Thompson and put Abreu back in RF. Lineup could look like this:
CF - Carey
LF - Palmer
C - Collins
RF - Abreu
DH - Thompson
SS - Hernandez
2B - Lopez
3B - Ruiz
1B - Fieger
That's how I'd do it anyway. To be honest, I would even maybe flip Thompson and Fieger in the batting order for the first few games Thompson is back, just to ease him back in at the bottom of the lineup. In an inning where you have to face 9-1-2 (Thompson-Carey-Palmer), that would be challenging for a pitcher to face, and then head into appearances by Collins/Abreu to follow it up. Could potentially set up a big inning in that situation.