Brendan Rodgers claims Celtic's Europa League hopes were taken away by German referee Deniz Aytekin in the 1-0 defeat by Valencia in the Mestalla.
The Spanish side impressed in their 2-0 win in the first leg of the last-32 tie in Glasgow last week, but were second best in front of their own fans until the 37th minute when German right-back Jeremy Toljan, on loan from Borussia Dortmund, was sent off for picking up the second of two bookings for a foul on Goncalo Guedes.
The 10-man Hoops kept going valiantly but were undone in the 70th minute by a goal from substitute Kevin Gameiro which gave the home side a 3-0 aggregate win.
Afterwards Rodgers said: "Yes I thought we were much the superior team up until that point. I think our shape and everything worked really well for us.
"We started the game ever so well, nice and tight defensively, pressing at the right times. We had confidence not just to keep the ball but we carried a threat in our penetration. It looked like we were going to get that goal we craved.
"I thought the referee took the game away from us, so that was disappointing. I thought the players came together but I didn't think it was a second yellow card.
"I thought it was a free-kick to us because the player has come on the blindside and sort of made contact with Jeremy.
"That changed the dynamic of the game but even so the bravery of the players was incredible, they kept going.
"I spoke to him (Aytekin) just after the game. He said it was a definite sending-off. I thought it was really harsh. You just sensed we were building into the game and it was disappointing.
"That was a key moment that took the game away from us. It's unfortunate.
"The players tired a little bit towards the end but still we could have done better with the goal. But the difference over the two games was that in the key moments in the game we haven't defended so well.
"But overall I thought we were excellent, I was very proud of the team."
The Scottish champions were knocked out at the same stage of the tournament last season by Zenit St Petersburg.
Asked about that stage of European football perhaps being a glass ceiling for the Parkhead club, the Northern Irishman said: "You are always looking to improve.
"It's maybe difficult for us. But we can't give up hope. You saw the team play very, very well tonight. We have to look to qualify for European competition again next season and try to progress.
"The performance tonight, our supporters will be very proud of the team, having that courage to come and play and force the game against a very good side.
"I said last week that we started the game well but if you make mistakes at this level you'll get punished. Unfortunately for us, that's what has cost us."
