But the Bairns boss on Tuesday gave them his full backing as they bid to atone at home to Motherwell on Wednesday night.
"The players are professional enough and they know I back them 100%, and they certainly back me 100%," May said.
"At no point could anybody ever say they were going to put in a performance like that, but these things happen in life and one thing I know is that they will be more than determined to make that up.
"Everybody is disappointed but we are still a point off where we want to be at the end of the season, and I'm sure this group of players will help the club do that.
"They are fully committed, they just had a bad day, which sometimes happens. It just so happened that so many of them had it on the one day.
"The players over the last couple of months have done extremely well and I'm sure they will go again and do extremely well."
May's post-match comments were out of keeping with his early-season approach when he continually praised his players throughout their 11-game wait for an SPL run.
So he feels they will understand his words came out of frustration after the same 11 players who drew at Celtic Park the previous week produced arguably their worst display of the campaign.
"I don't think I need to put spirit back into any of the players," May said.
"They have got their own personal ambitions and the one thing they know, I will back them 100%.
"If I criticise them, I must really mean it. I give them a lot of praise.
"The players are fully focused and they give me 100% every day. It was unfortunate we never did what we are good at on Sunday.
"The number of games we've had and the goals we lost at vital times contributed to the overall performance.
"We just have to get on with it and I'm sure the players will respond in the right manner."
The Falkirk manager is confident captain Darren Barr will be fully focused after signing a pre-contract deal with Hearts on Monday.
May feels the defender will benefit from ending the speculation over his future after holding talks with Hibernian, Aberdeen and Dundee.
May said: "At the start of the season when Darren said he was willing to see out his contract, we knew we were going to lose Darren.
"I've no fear that Darren has already signed for another club because he will give you the same commitment week in, week out.
"I'm grateful that Darren has been here for 10 years and we
wish him all the best.
"It's been very frustrating for Darren, a lot of things have been in the paper and maybe Darren thought he was going to get asked to leave the club. That was never going to be the case.
"No club came up with a package that was right for Falkirk or Darren."
Source: Team Talk