Claudio Ranieri blamed Mike Dean's failure to spot a handball in the build-up to a Sam Vokes strike for Leicester City's 1-0 defeat to Burnley at Turf Moor.
Clarets striker Vokes, on as a second-half substitute, appeared to handle the ball before scoring an 87th-minute winner that earned Burnley their fifth consecutive home victory in the Premier League, but referee Dean allowed the goal to stand.
Ranieri praised his side's determined performance and claimed a draw would have been a fair result.
When asked whether he thought Vokes handled the ball before scoring, he said: "It was a handball. It was a handball to everyone watching on TV but not to the ref and he's the boss so we lost the match.
"It's very hard to lose this match but it's okay.
"I think we deserved to draw but they played right to the end and well done to them."
Leicester had a second-half penalty claim turned down when Jamie Vardy went to ground under a challenge from Tom Heaton, but Ranieri said his players needed to show more composure in front of goal.
The Foxes host Manchester United in their next Premier League fixture and Ranieri said: "We have to react as soon as possible.
"The performance was good. If we were a little more calm on the counter we would have had the chance to score but we were so frenetic and trying to do everything right and we made a mistake on the last pass."
Victory over Leicester capped a significant day for Burnley, who announced at half-time that Robbie Brady had become the club's record signing for a reported £13million.
Following the transfer deadline day arrivals of Brady and Ashley Westwood from Aston Villa, boss Sean Dyche said: "Slowly but surely we are trying to build and I think we've put some of the building blocks in the right place.
"It's not an easy task but we continue to add at an appropriate level to the club so it can move forward.
"Different types of quality. We need a squad with depth that can compete. They are quality players but I think I've got a lot here."
On condemning the Premier League champions to their third successive league, Dyche said: "I know they've had an up and down time this season but they're still a very good side. They've got players who can affect the game, particularly in the attacking positions. I thought we dealt with their threat very well.
"We kept knocking on the door all night and eventually got a break for the goal."