It was initially thought that Dilshan had just a badly-bruised thumb after being hit twice by Chris Tremlett in the second Test at Lord, it was revealed he suffered a hair line fracture.
Sri Lanka team manager Anura Tennekoon has confirmed the injury which means he will miss the final Test at the Rose Bowl with Kumar Sangakkara will captain the side in his absence with Sri Lanka needing a win to tie the series.
Tennekoon said: "He definitely won't be playing.
"The main reason we've kept him out of this Test match is that, had he played and got another blow while fielding on that thumb, he might have been out for the rest of the tour.
"So as a precautionary measure, we have kept him out."
