When a young hurler does anything to his shoulder, the red flags are hoisted (often at half-mast, just to be sure). In Feliz's case, he went to the DL last May with shoulder inflammation, and as a minor-leaguer he suffered similar problems in 2009. With that said, though, it's spring, and Feliz is of course in the midst of transitioning from reliever to starter. As he gets stretched out, some shoulder soreness is to be expected. So far, that's all it appears to be. Given Feliz's age and history, the situation bears watching, but there's no cause for panic.
From the Rangers' standpoint, they can pump the brakes with Feliz because they have the deepest rotation in the game. If Feliz can't go, then Alexi Ogando can. Or Scott Feldman. Or, soon enough, Martin Perez. That's a luxury that will allow Feliz to develop as a starter at a more comfortable pace. He'll be the better for it.