London Irish director of rugby Brian Smith was "gutted" after his side threw away an 11-point lead to lose at home to Exeter.
The visitors rattled on 17 unanswered points in the final quarter, including tries to Dean Mumm and Ben White, to secure a 29-23 success.
For the opening hour Irish were the better side, showing greater enterprise than a lethargic Exeter and with visitors' wing Tom James in the sin bin, the hosts appeared sure-fire winners.
Irish had already gone over through Nick Rouse and Marland Yarde in each half but they came to a standstill as 19 points from the boot of Gareth Steenson ensured Exeter sailed home.
"At the back end of the match we couldn't defend our errors, we needed to bring our error rate down but we didn't eliminate those errors and they came back to bite us on the backside," Smith said.
Irish overcame their crippling injury list to be well in control after 60 minutes but eventually those injuries told.
The Exiles lost Topsy Ojo in the warm up and forwards Jebb Sinclair and Halani Aulika during the course of the match.
"We went into the contest with quite a few hiccups but we were well prepared and that showed for the first 60 minutes, but their first try was a momentum changer as we lost all our momentum after that," Smith said.
"Halani Aulika's injury could be a serious one it is an Achilles which may be ruptured. We will assess it in 48 hours but potentially it was a season ending injury."
Despite their win, Exeter boss Rob Baxter conceded they were not at their best.
"I am not happy with our performance but we showed great character," he said.
"In the first half we were disappointing for our game wasn't direct enough as we were content to try and pass the ball around the opposition."
The Exeter coach also conceded that the Chiefs had not displayed their best form so far this season.
"We are stuttering along a bit, we haven't really hit the heights that we reached a year ago but we are going well in training," he said.
"The first four or five weeks of the season are a dogfight and you just have to fight for the whole of the 80 minutes to get what you can.
"After the first four weeks you can draw breath and assess where you are."
Exeter also have players on the injury list as Baxter stressed.
"We are missing the likes of Jack Nowell and Luke Arscott who got us on the front foot last season but Phil Dollman did a lot of good things for us at full-back while late replacement flanker Ben White was fantastic," he said.