Celtic manager Neil Lennon accused the referee of favouring Juventus after a series of penalty-box tussles went unpunished in their Champions League last-16 first leg.
Celtic were ruthlessly taken apart in a 3-0 defeat in Glasgow on Tuesday as the Italians soaked up everything the Scots could throw at them and counter-punched their way to a substantial first-leg lead.
It was the persistent pushing and shoving at corners and free kicks that irked the Glasgow club and sparked a post-match debate after Spanish referee Alberto Undiano Mallenco chose to warn players rather than give the hosts a penalty.
"I thought he (the referee) was poor," Lennon said on Sky Sports. "I thought he was very pro-Juventus. I was disappointed with his performance to say the least."
He added: "It's not rugby we're playing, it's soccer.
"I pointed it out to the referee at halftime in the tunnel area but he just waved me away. I made it clear to the players to flag it up to the referee in the second half but he ignored our requests.
"They were being fouled, manhandled. Every time one of my players tried to move he was held. He should have given a penalty on at least two occasions.
"I'd like to know what the interpretation of the rules are in Italy or Spain, because it's blatantly different to what they are in Britain from what I've seen tonight. They were fouling on every opportunity and he was staring right at it. So are the rules different in Spain? Because, on that showing, they must be."
Stephan Lichtsteiner was involved in a long-running tussle with Celtic striker Gary Hooper, with both receiving yellow cards in the first half.
The Juventus defender seemed more intent on keeping Hooper away from his goalkeeper Gianluigi Buffon than making any attempt to defend the ball.
"It's normal," Lichtsteiner told Sky Sports. "I think it is part of football that they play the corners and the free kicks, and of course they score more than 40 percent of their goals in the Champions League from free kicks, and they look to block the goalkeeper.
"It was my role today to keep him away from Buffon.
"A penalty for what?" he added. "It is more a foul from him than for me because if you attack the goalkeeper it is a goal."
Celtic took a different view with midfielder Kris Commons questioning how the additional officials UEFA employ behind the goal failed to spot any offence.
"You've got a referee there, a guy behind the goal, a linesman - the whole idea of the official behind the goal is to look out for this sort of stuff," Commons said.
"If he can't identify when people are being hauled, manhandled, wrestled to the floor then I don't think he should be in a job."
Celtic right back Mikael Lustig added: "They used a lot of arms when we got our corners but it is up to the referee. Of course we tried to speak to him but he didn't listen to us."
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