CELTIC took disciplinary action against Efe Ambrose in the hours before last night's Champions League exit to Juventus after the defender missed the team bus to a training session and had to make his own way there in a taxi.

Manager Neil Lennon insisted the Nigerian internationalist was not dropped for the 2-0 defeat in Turin because of that – Ambrose was a substitute and played only in the second half – but his anger was obvious as he was reluctant to answer questions about the 24-year-old's behaviour. Celtic went out 5-0 over the two legs, their heaviest aggregate defeat in Europe, and Ambrose's personal horror show continued when he missed a fine chance to score with a header. Ambrose has been an important player for Celtic this season but he was at fault in two of Juventus's goals in the first leg and, earlier in the campaign, had almost missed the team's flight to Barcelona after forgetting his passport.

"There was disciplinary action taken against him," said Lennon of yesterday's incident. "The bus left without Ambrose when he failed to appear on time. It wouldn't have affected the team selection [last night]. Is this the best line of questioning you can do here? Are we not going to talk about the game? Are we going to talk about things that aren't important?"

Goals from Alessandro Matri and Fabio Quagliarella finished Celtic off in the last 16 and, although they were competitive and made chances in the Juventus Stadium, they could not live with their hosts' class. Lennon admitted it will be difficult to retain all of the players who qualified from the group stage and defeated Barcelona at Parkhead. Gary Hooper and Victor Wanyama have declined to sign contract extensions and are wanted in England.

"That's going to be very difficult. I think some of them want to progress their careers maybe out of Scotland," he said. "It's difficult to stop that progression. We are doing our job, we are bringing these young players in, developing them and hopefully selling them on for significantly more than what we paid to bring them in.

"We have already offered contracts to a couple of players that you know of already. You know that those contracts have been knocked back so far. We'll try to go back and work on that but the environment we play in means it is always difficult to keep them."

Lennon acknowledged that Celtic could not live with Juventus over the two legs. "You always want more. I think over the two games we played very well but we were just a little bit short in some areas. There is no disgrace in that. Juventus are a fantastic team with a great work ethic.

"The difference is the quality in the final third. We played some really good football, we had really good spells in either half but we missed what were really good chances to win the game, or to get back into the game. The difference is quality. Quality counts. It might be a handicap that we are probably about £100m behind most of the other squads in the last 16 of the Champions League.

"The difference is that the bigger clubs have far more significant spending power and stronger squads. You only had to look at Juventus' bench to see how strong it was, allied to the ones already on the pitch.

"I don't see any reason why Juventus can't win the Champions League. I hope they do, I sincerely mean that."