ESPN.com's Eric Karabell, who writes about fantasy baseball, took a look at some closers who have changed teams this offseason (insider). He lists Joakim Soria as a player to keep an eye on. Part of what Karabell writes:
He's more interesting for keeper/dynasty formats, as he could miss half of 2013 recovering and Nathan could be elsewhere by 2014, so pay attention to this situation.
You'll have to read the rest to see what else Karabell says and the other closers he thinks are worth watching (insider).
Soria could be in position to get a few saves this year as he would close when Nathan isn't available. And while Nathan could be somewhere else by 2014, that depends on 2013. Nathan has a $9 million club option. If he pitches in 2013 like he did in 2012, expect the Rangers to take that option. But Karabell is right: Soria is in position to move up to closer if something happens. So if you've got a deep keeper league and plenty of bench spots, he's not a bad guy to stash for future years. But for 2012, don't expect a bunch of fantasy points.