Joe Cole has said Chelsea appeared to be hindered by fatigue in Tuesday's 2-1 defeat at Wolves.
The Blues went ahead early in the second half through a goal from Olivier Giroud but squandered their lead in the last 20 minutes of the match, as Daniel Podence's effort took a deflection before evading Edouard Mendy for the equaliser.
Pedro Neto then sealed the three points for the hosts when he latched onto a pass from substitute Vitinha before smashing into the bottom corner deep into stoppage time.
The defeat was the London side's second in a row in the league, having gone down 1-0 at Everton on Saturday.
Chelsea boss Frank Lampard admitted that his side were showing signs of fatigue during Tuesday's game, but insisted that is no excuse for the result.
His former team-mate Cole also sensed a lack of energy towards the end of the game and believes they may need to make some changes ahead of their home match against West Ham next Monday.
"I think Chelsea, when they analyse that second half, will kick themselves," the former Chelsea and England player said on BT Sport.
"Particularly Neto's goal because they've lost their shape in attack. The game was getting end to end and Wolves looked like they had the fitter, stronger, athletic team.
"You have to take into consideration [Chelsea] have had a fantastic Champions League campaign.
"I think Frank might have to look at this and take a view of some players who looked a bit leggy.
"Everton was a bump in the road, I think this is a bigger bump in the road. I don't think it's one of those you worry too much, but maybe tweak a few players here and there. In this game they looked a bit jaded."
The Stamford Bridge side are fifth in the Premier League after 13 matches and trail leaders Tottenham and Liverpool by three points before those two sides face each other at Anfield on Wednesday evening.
After next week's clash against West Ham, Chelsea will visit London rivals Arsenal before hosting Aston Villa at Stamford Bridge in their final game of 2020.