The hosts were condemned to their ninth defeat in 12 games after Barrie McKay’s second-half winner at the Keepmoat.
“It’s frustrating and disappointing again,” admitted Butler. “It seems like we’re saying that every single week.
“One mistake led to the goal and then you’re fighting an uphill battle. Once Fleetwood got their goal they saw it out.
“We lost too many individual battles. They overran us.
“It’s so frustrating whether you’re on the pitch or on the sidelines. We’re not doing the basic stuff right. We give them all the information they need, but they just aren’t applying it on the pitch.”
Player-manager Butler did well to clear Sam Finley’s chip off the line. And the visitors were let off when striker Kyle Vassell fired against the post.
But the pressure told six minutes into the second half as McKay raced in off the wing and superbly fired home from a tight angle. Former Rotherham striker Vassell came close to immediately doubling Doncaster’s deficit.
Reece James had the hosts’ best chance at salvaging something from the game when he found the side netting.
Down the other end, Callum Camps should have put the game to bed when he blasted wide of the mark. Louis Jones produced a good late save to keep out Ged Garner, but it wasn’t enough to spark a last-gasp revival.
Doncaster Rovers: Jones, Wright, Anderson, Butler, James, Smith, Robertson (Bostock, 45), Sims (Horton, 75), Richards, Okenabirhie, John-Jules (Coppinger, 63). Unused subs: Bottomley, Gomes, John, Greaves.
Fleetwood Town: Cairns, Donacien, Hill, Connolly, Andrew, Biggins, Rossiter, Finley, Camps, Vassell (Garner, 76), McKay. Unused subs: Coleman, Whelan, Sheron, Baggley, Feeney, Duffy.
Referee: Sam Barrott (Huddersfield)
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