I had went back to DVR to check out the last 7 minutes of the game or so. Here are some noticeable possessions that involved Rondo.
Between 6:30 & 5:30 remaining, Rondo had two possessions I'd deem poor. 1 was a bad pass that resulted in an out of bounds. The 2nd was an off-balance floater he tried to take from the left side and bank over Gasol.
With roughly 3:20 remaining, Rondo had another bad possession where they worked the shot clock too long.
With 3:00 remaining, Rondo had that travel called on him.
With 2:00 remaining, Rondo made a great pass to Perkins who was fouled on the play and converted 1 of 2.
With 1:30 remaining, Rondo missed a jumper what arose out of a slowed down offense set started by a Pierce ISO.
Remainder of the game were that Pierce/ISO stuff we've grown accustomed to.
So I'd say there is some merit that Rondo struggle a bit down the stretch. He made a couple of bad decisions and seemed to have cooled off.
Rondo had a heckuva game but I don't think its inaccurate to say that he faultered a bit down the stretch.