Celtic suffered a hugely disappointing 4-1 defeat at home to Sparta Prague in the Europa League on Thursday evening.The Scottish giants found themselves 2-0 down at half-time before Leigh Griffiths pulled a goal back for the hosts in the 65th minute.Ten minutes later, however, Luka Julis completed his hat-trick for the visitors, who added gloss to the scoreline in the closing stages thanks to Ladislav Krejci’s strike."This is definitely a turning point - it won't happen again, that's for sure," Celtic boss Neil Lennon, furious with his team’s performance, was quoted saying by BBC Sport."We can't accept that and the players know that as well. I can't defend the players. I've tried to over the piece, but I can't defend them tonight."p1eme513471lqq1goc1jfm14el4o9.jpgLennon’s first substitution of the evening saw Mohamed Elyounoussi go off in place of Griffiths in the 59th minute.Elyounoussi, 26, was then caught looking at his mobile phone in the 83rd minute by TV cameras.p1eme538gu1g9n1luocrs1e30m6nb.jpgLennon was told about this during his post-match interview, per the Daily Record, and warned: "He better not have been. That’s something I’ll deal with."Former Celtic striker Chris Sutton, meanwhile, was fuming with Elyounoussi on BT Sport and says he would fine the Norwegian winger two weeks’ wages if he was in Lennon’s shoes.“What I question is the players’ commitment,” Sutton said. “There’s a player sitting in the stands this evening on his mobile phone, that is totally, totally unacceptable!“That’s scandalous. Is he committed to the cause, is he committed to the club? Totally unacceptable.“I’d fine him two weeks’ wages for that.”

Strong words there from Sutton, who was already angry with his former team’s display.

“That was one of the most gutless displays from a Celtic team,” Sutton added. “I know a lot of Celtic fans are saying Europe doesn’t matter this year, I’m sorry, it absolutely does. You play for Celtic, you want to compete in Europe

“Celtic quite frankly did not compete in any way, shape or form. It’s a dressing room where you have to question a lot of the players, a lot of the characters.

“We see Leigh Griffiths come on the pitch, get his goal but I look at his attitude all season and I think Leigh Griffiths is a brilliant option for Neil Lennon – he can’t be bothered to get himself fit. He sums this Celtic dressing room up.

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“I thought they chucked it. They were patchy in the first half, had a little spell in the second half but they bottled it.

“That quite frankly isn’t good enough. There’s a way to lose a game. Teams feel they can get at Celtic and this Sparta Prague team battered them.

“Pathetic, pathetic. I haven’t seen this bad a display in a long time. It was bad enough against Rangers but this was a step down if at all possible.”