But it's clearly not clever tennis.
It's just being over-tentative. He still has the power to hit winners left and right but he's not taking chances as much any more.
I think that's just lack of confidence in stroke production, last year I lost count of how many times I saw him ballooning his forehand wide or long when he tried to pull the trigger. He doesn't want to lose matches by erroring himself to death, which to a certain extent happened again tonight; most of his rallying was passive, but when he fell behind in the final set there was his usual patch of play where he hits a flurry of wide forehands, shanked backhands, the full repertoire of sprayed strokes.
Being so cautious in matches is clearly a double-edged sword, he gets more free points on serve but the defensiveness only prolongs matches that he would have won a lot more easily in his prime. Take the last three Wimbledon finals for example, where he's managed 5 breaks of serve in 15 sets and went something like 63 return games in a row between last year's final and this year's without breaking serve. It's not energy conserving to need more than 4 hours just to get a break. The sets that he's won in those finals: 7-6, 7-6, 6-2; 7-6, 7-6; 7-6, 7-6, 16-14.