The Champions Trophy has been England’s first tournament since Brendon McCullum combined the white-ball job with his role as Test coach.
The New Zealander, who backed Buttler to remain as captain when being appointed, said he thought his skipper was considering quitting in the immediate aftermath of the Afghanistan defeat and Buttler confirmed his decision at the team hotel on Thursday.
“He sent me a message saying he needed a chat, and I knew then that things were coming to an end,” McCullum told BBC Test Match Special.
“When he told me he wanted to step down, I was initially thinking, ‘Don’t worry about it, we’ll carry on’ but no, he’s made the right decision.”
Buttler’s recent record has been poor but he has also had to deal with his best players often being absent from squads as Ben Stokes’ Test team was prioritised.
“He has worn the captaincy quite heavily because he cares so much about playing for the shirt, the guys in the dressing room and all the supporters of the team,” added McCullum.
McCullum said he will begin discussions with managing director of men’s cricket Rob Key over a successor in the coming weeks.
Batter Harry Brook, all-rounder Liam Livingstone and opener Phil Salt have all captained the white-ball team in the past six months.
Brook, who was made Buttler’s vice-captain in January and led in five ODIs against Australia last year, appears the favourite.
“This news is still pretty fresh,” said McCullum.
“We have got time after this tournament as we go into the English summer so we can work out who the right person is.”
Buttler has captained England in 44 ODIs overall, with a record of 18 wins, 25 defeats and one no result.
He holds a better record as captain in T20s, with 26 wins, 22 defeats and three no results in his 51 matches in charge.
