The tourists were thrashed in Colombo on Tuesday after sealing the five-match series with a game to spare.

Tom Curran and Moeen Ali dropped simple chances and players berated each other after several misfields.

"We've got some hard work to do going forward," Bayliss told BBC Sport.

"Our performance in the field, our attitude in the field, was nowhere near up-to-scratch for a number one team."

After Sri Lanka posted 366-6 - their highest ever ODI score against England - the tourists slumped to 4-3 in the first 10 balls in reply before reaching 132-9 when heavy rain caused the match to be abandoned.

"Fielding is an attitude - you want the ball to come to you, do the simple things right, anticipating and not waiting for it to go past an inner-ring fielder," said Bayliss.

"Fielding can give you confidence for the rest of your game - it's the one thing that we all do together, but we weren't on our game and that showed and passed over into our bowling and batting performance."

England made three changes for the fifth ODI, with captain Eoin Morgan rested and seam bowlers Sam Curran, Mark Wood and Liam Plunkett playing for the first time in the series, but all three were expensive.

England, the world number one ODI side, are favourites for the 2019 World Cup in England and Wales, having won their last nine series' of two or more matches and winning 41 of their 54 fixtures since June 2016.

"Come World Cup time, we're going to need more than 11 guys in form so it was an opportunity to give some of those guys a little bit of game time," said Bayliss.

"It's one thing giving guys an opportunity, but what we're looking for is some of those guys to take hold of that opportunity. If they do - they might find themselves in a World Cup squad, and if they don't well they might miss out.

"There are not too many more opportunities before the World Cup squad is picked, so some of the guys will have to turn it around pretty quick."

Morgan, who was named player of the series, said defeat was not a setback in England's World Cup preparations.

Bayliss said his side will "turn a bad performance into a good one next time" and could take confidence from how they adapted to conditions in securing a 3-1 series win in Sri Lanka.

"The conditions are going to be different than what they are in England and I think we showed we have got adaptability throughout those first three or four matches, so that was a positive."

England face Sri Lanka in the sole Twenty20 on Saturday before the three-Test series starts on 6 November.