C'mon, when you drafted Huston Street, you had to know there would eventually be a news item like this one:
Street has a groin problem. He said he first tweaked his groin last weekend in Texas, and he felt it got worse after a game against the Tigers early in the week. Street said he has lost a little velocity because of the injury, but he can still pitch ... I wouldn't be surprised if Street winds up on the disabled list.
That's from the Press Democrat's Jeff Fletcher. If Street does, in fact, find his way to the DL, Keith Foulke seems like the A's reliever most likely to get save chances in his absence. Foulke has a 2.79 ERA and 1.29 WHIP through 19.1 innings this season. He also has five holds and 15 Ks. Fletcher mentions both Foulke and Alan Embree as candidates.
If you're speculating on future saves and can make only one add/drop, Foulke is the guy to target, based on year-to-date performance and usage. However, before adding the 1.3 percent-owned Foulke, you should also grab the 9.5 percent-owned Santiago Casilla and stash him on your fantasy DL. There are some very encouraging notes on Casilla's player page right now. This quote is all you should really need:
"I'm throwing 100 percent."