Buttler’s last major contribution for England was 83 from 30 balls against South Africa in September but, given his illustrious career, his place in England’s XI remains secure.
He scored 97 not out for Durban Super Giants in the SA20 in January but made 12, 20, 15, 22, three and one in his other innings there.
“I felt I was playing really well in the SA20 without getting scores,” Buttler said. “One thing I always pride myself on in T20 is if you get in, go and make a good contribution.”
Buttler and England trained on Thursday for the first time since their win over Italy on Monday, after travelling to Sri Lanka.
Buttler had a lengthy regular net practice and then faced throw-downs from fielding coach Carl Hopkinson with a wet tennis ball on a soaked concrete strip – an apparent attempt to sharpen his reflexes.
Team-mate Jacob Bethell dismissed any doubts about the opener’s form.
“He’s fine,” Bethell said. “The options he has taken haven’t come off but no one in that side is worried about Jos in terms of performance.
“He will come good when we need him in the big stages of this tournament.”
Bethell trained with a bandage on a finger on his left hand. He suffered a cut during the win over West Indies and it has meant he has been unable to bowl.
The injury will be assessed again before England play co-hosts Sri Lanka in their first match of the Super 8s phase on Sunday in Pallekele.
They progressed through the group stage in unconvincing fashion with edgy wins over Italy, Scotland and Nepal, plus a defeat by West Indies, but before the World Cup they beat Sri Lanka 3-0 in a T20 series, with all three matches played in Pallekele.
“To beat a good Sri Lankan team at home in their conditions 3-0 was a massive confidence boost for us,” Bethell said.
“You can feel it within the group the boys are confident coming back here.
“We know the conditions, we know how a couple of the teams are going to play. We’re definitely, definitely very confident about this Super 8s.”