Alan Pardew bemoaned the short time between fixtures as his West Brom side narrowly lost 2-1 away to West Ham on Tuesday night.
A brace from Andy Carroll, including a 94th minute winner, cancelled out James McClean's early effort to pile more misery on the Baggies.
Speaking to Sky Sports, Pardew said: "the two-day turnaround cost us in the end, we just ran out of legs.
"We just couldn't keep going and to concede in that manner is absolutely heartbreaking for the players."
West Brom went into the break 1-0 up after McClean's hugely deflected goal looped over Adrian's head. But their performance in the second half was a shadow of their efforts in the first.
West Brom have now gone 20 games without a PL win - no other PL side has gone more than 9 games without 1 this season— Sky Sports Statto (@SkySportsStatto) January 2, 2018
Now the longest winless run of any PL side over last 10 seasons (passing Aston Villa's 19 games in 15-16)
Longest run since Derby's 32-match run in 07-08 pic.twitter.com/WABawAPQNv
"We should've done a bit better second half, but we did good in the first half, we were probably the better side.
"But second half we conceded a bit too much for my liking and unfortunately we've been undone."
The dying minutes of the game proved to be thrilling as both sides looked to snatch a final winner, but Pardew said that maybe accepting a point would've been the wiser decision.
"We perhaps should've taken it to the corner and grinded out a point, but we're under pressure to get a win and we'd committed players forward.
"In that scenario when you're under the pressure we are and the run we're on, I can understand it. I'm frustrated that we've done that but I can understand it."
West Brom had less that 48 hours rest before the fixture, having faced Arsenal on New Year's Eve, with the tiredness of the Baggies players showing on several occasions throughout the game.
"It was a bit unfortunate to lose Matty Philips in the warm-up, that just shows you the pressure we're under in the two games.
"We had players hanging at the end, [Craig] Dawson hasn't played a lot of football, how he got through the second half I don't know."
"With two day's turnaround, some of the effort we put in was amazing."
When asked about the incident involving Jake Livermore, Pardew was reluctant to speak heavily on the matter.
The England international was ushered down the tunnel after a confrontation with some home fans after he'd been substituted
"He wouldn't have gone into the crowd unless he was provoked."
The result still leaves West Brom 19th in the Premier League table, only above 20th-placed Swansea on goal difference.