England captain Alastair Cook has played down speculation surrounding Jos Buttler and the Test team.

In recent months, reports had claimed that the wicket-keeper would feature in the upcoming five-day series with Sri Lanka, and the clamour grew yesterday with his knock of 121 in a one-day international against the same opposition.

However, Cook believes that the 23-year-old still has improvements to make before he can be considered for the longer format of the game.

"He's certainly found his method in one-day cricket. He knows what he's doing. I think he's yet to find that in four-day cricket," said Cook. "I think he'll be honest with himself, he needs more time to do that. But a guy who is as talented as that, there's no reason why he can't.

"I think he will become a very good Test player at some stage for England. Talented people find ways to do that, but I don't think he's quite ready yet for that role."

Providing that he can prove his fitness, it's expected that Matt Prior will take the gloves for the Sri Lanka encounters.