Callum McGregor described Celtic's display against Ferencvaros as "nervy" after they began their Europa League campaign with a 3-1 defeat at Celtic Park on Thursday. 

Ferencvaros took a 20th-minute lead through Bamidele Yusuf before Mika Baur hauled the Scottish Premiership champions level just a minute before half-time. 

However, the visitors would go into the break ahead as Kristoffer Zachariassen neatly flicked past Viljami Sinisalo in first-half stoppage time, after Yusuf's mazy run. 

It got even worse for Martin O'Neill's side two minutes after the restart when Daniel Arzani, who spent two seasons on loan at Celtic between 2018 and 2020, picked out the top-right corner with a sensational finish. 

Celtic have now lost five of their last seven home games in major European competitions (W2), conceding an average of 2.4 goals per game in those matches.

Ferencvaros, meanwhile, ended a run of four away games in major European competitions without a win (D1 L3) since a 3-2 win against Salzburg in the Europa League in October last season, though McGregor acknowledged his team were way off the pace ahead of Sunday's Old Firm clash with Rangers in the Scottish Premiership.

"It was tough. They scored at good times. It's a sore one, but we have to stick together now," McGregor told TNT Sports. 

"It's a little bit broken, a little bit nervy, but we have to fight our way through this. The only way through it is hard work.

"It's a tough period. You can see how quickly it comes down on top of you. It's a relatively new group, so we have to learn. You don't get much leeway.

"The ultimate test at the weekend is that we have to win the game. It's about staying together, putting one foot in front of another, and we just need another bit of luck."

Celtic's latest defeat comes off the back of another Old Firm derby in the Scottish League Cup last Sunday, as they lost 3-0 at home to Rangers.

Against Ferencvaros, Celtic finished with an expected goals (xG) total of just 1.04 from their 16 shots, compared to their opponents' 0.98 from 14 attempts at goal.

O'Neill bemoaned the lack of risk-taking in his team's play, even saying that Celtic were taught a "European lesson" by Ferencvaros. 

"It's a huge frustration, obviously, but it's also psychologically quite damning as well," O'Neill added. 

"Just when you've fought your way back into the game, and you think, well, at least defend properly, and we didn't do that.

"That was really disappointing. It's not the start we wanted. We have seven games in which to try and get some points on the board.

"Really need to concentrate now on Sunday. It was, I think, a European lesson for us in many respects. We'll get ourselves together.

"We need to re-energise ourselves as much as anything else. When we have decent possession of the ball, just don't give it away.

"But I also think it's about taking a few risks as well too – risks in the proper areas of the field."