Last night, Joe Nathan pitched the 9th (and final) inning of an 8-2 victory over the Tampa Bay Rays.
That was significant, as it was the 55th game that Nathan has finished this season, which means that Nathan has the right to void the Rangers' team option for the 2014 season.
The Rangers' option is for $9 million for 2014, and there's a $750,000 buyout which Nathan would forfeit if he opts out. However, my guess is that Nathan will more likely than not go ahead and void the option year, as I'm guessing he will almost certainly get more than $8.25 million guaranteed in his next contract.
The Rangers have Joakim Soria, Neftali Feliz, Alexi Ogando and Tanner Scheppers all under team control for next season, so it wouldn't be surprising if they let Nathan depart after the season without pursuing him aggressively. Soria, in particular, appeared to be a guy signed with an eye towards having a replacement ready for Nathan after 2013.