David Moyes summed up Sunderland's 4-1 drubbing at Burnley in two words: "Defensive frailties"
Sunderland were taken to the cleaners by Andre Gray who netted a hat-trick for the Clarets who pulled nine points clear of the relegation zone at Turf Moor.
Ashley Barnes added the fourth from the spot in the 67th minute after Seb Larsson conceded a penalty for a silly challenge on on Scott Arfield.
Jermain Defoe pulled a goal back 19 minutes from time but it was of no consolation to the Black Cats who missed the chance to climb out of the bottom three.
"Defensive frailities," said Moyes when asked why Sunderland had collapsed to their heaviest away defesat of the season.
"We couldn't really cope with a bit of good old fashioned English style balls forward, over the top or down the channel.
"We didn't deal with that at all well.
"The first goal, two of them go for the same ball and neither of them won it.
"I think we should have saved it as well."
Moyes believes the 24th-minute loss of Lamine Kone with a hamstring problem was a hammer blow to the Black Cats and a major contributory factor to the defeat.
The central defender was hurt when sliding into the advertising hoardings in the 18th minute as he tried to make a block on an Ashley Barnes cross.
He continued, briefly, after treatment but his departure proved crucial.
Gray got the first in the 31st minute when John O'Shea, who had started the game in midfield, went up with Papy Djilobodji for an aerial challenge with Barnes.
The ball skimmed O'Shea on the head before reaching Gray who beat Vito Mannone from 18 yards.
Gray got away from Djilobodji for his second six minutes into the second half, Mannone coming out and making a weak effort at stopping the forward, who sidestepped him before finding the empty net.
The killer third came in the 53rd minute when sub Steven Pienaar trod on the ball and Burnley got possession forward with Barnes setting up Gray for his treble.
"I thought we had started relatively well," said Moyes, who lost Victor Anichebe at the end of the first half, also with a hamstring injury.
"There was nothing in the game but losing Lamine was a big blow.
"We had to organise before the game after losing Jason Denayer and we had to re-organise again."