He is in no way capable of beating Alonso, that's just not possible, I mean come on, he has not been able to defeat him in 2 seasons in the same car. What makes you think he will defeat Alonso by joining an inferior team (he is not to join Red Bull or McLaren, is he?)?
I have stated this many times and starting to sound like a really stupid fanboy, but it's a point many disregard. Is that Massa would have been less than a win behind to Alonso if you give him the Hockenheim win, and before Hockenheim he had a string of 3 bad races which he really should have scored points but through no fault of his own (bar one me thinks) he scored none.
Canada the incident with Liuzzi where their cars just kept hitting each other, he was then on for at least 8th place but then Schumacher chopped him and he needed a new front wing. Valencia, he had to queue behind Alonso, losing massive amount of time due to queing and Ferrari's ill timed pitstop. Silverstone, puncture in the first lap after Alonso collided with him, and for some odd reason pitted a one more time extra (bar the puncture).
Of course Alonso had some poor results too, but most of them in the first half of the season where of his own doing, unlike Massa.
He has also shown glimpses of himself this season I think, that being in China, and in Canada (before the mobile chicane Karthikeyan putting him onto the wet line causing him to crash) and ever since Ferrari have called off the title battle, he's been much closer to Alonso. Above that, he's had the worst pit strategies and pitstops this season.
I am damn sure there is still some of the "old Felipe" in him, it's just the psychological harm that his own team have inflicted on him. I really do fell for the guy.
And sorry if I have come across as a fanboy, but I analyse all of the drivers before I come to a judgement, and to say Massa has "under-performed in the past two seasons" I feel is an injustice as there is more to what meets the eye.