After his old club subjected his side to a 3-0 defeat, extending their winless run to seven games, the Cottagers boss has pinpointed a lack of fight as the key issue
A goal from Sandro and a second-half double from Jermain Defoe ensured that the home side failed to win yet again, a feat that the Cottagers have not managed since October.
The loss means that, despite a decent start to the season, Jol's side are slipping perilously close to the relegation zone as they are just five points clear of Southampton in 18th.
The Dutchman was keen to emphasise the importance of the first goal as he felt that disheartened his team, in spite of a good first half performance.
"I think it was a tight game first half, I think we probably had the better opportunities. We kept them quiet, we respected them. So I thought we played well, especially the first half," he told reporters after the match.
"The second half I feel that the first goal changed everything because we lost a bit of fighting spirit. Of course, it was a big blow. We couldn't score and they scored three so it was disappointing."
Jol spoke of his side's poor form and was eager to convey the need to turn their draws into points, as they have drawn four of their last seven games.
"We've had seven draws. That is too much - you need wins to get the points on the board. We had a lot of games - Reading, Arsenal, maybe even at Chelsea - where we could have nicked it and we didn't," he continued.
"We concede quite a few goals but, normally, if you score a lot, you can score four and concede three. But this was not the scenario, [though] in the first 57 minutes, we played well."