Rusty is one of the few true competitors left on tour. I mean I love Jo Tsonga but the dude is top 8 for awhile now and still has a very questionable mental game and he is far from the only one in the top 20 like this.
In the past few years Lleyton has had a lot of injury trouble, and yet when he returns and gets some matches in him, he's had decent results until the next injury. His AO last year was solid and he won Halle not too long ago beating Fed.
I think Lleyton wants to play (sooner than later of course) a full season without injury and see how he does. A full seasons for him of course will still be about 10 tourneys, but ideally with no injuries in between.