But Celtic manager Gordon Strachan heaped praise on Chris Killen despite his strike partner Scott McDonald's second hat-trick of the season in a 3-0 win over Motherwell at Parkhead.

Killen was surprisingly preferred to the Australia international for the lone striker's position in Lisbon on Wednesday as Celtic lost 1-0 to Benfica in the Champions League.

Both players teamed up in attack for the visit of Mark McGhee's side and win gained courtesy of McDonald took the champions three points clear of rivals Rangers at the top of the table.

Strachan bristled at the suggestion that his decision to rest McDonald in Lisbon had been vindicated before praising Killen for his part in the victory.

He said: "I don't have to justify myself to anyboy, just the players.

"I said the priority was the SPL. I would have loved to have played Scott the other night but he has had a lot of hard games.

"But I don't have to justify myself.

"He wouldn't have scored it if he hadn't had Chris Killen playing alongside him.

"I thought he was excellent. Last season, if Jan Vennegoor of Hesselink was injured we couldn't have played the way we did today, but Chris Killen allows us to do that.

"So I would say he was the most important person in the team for us today."

McDonald looked sharp against his former club, scoring the opener three minutes before the interval with a close-range header.

His strike just before the hour mark and an 87th-minute penalty gave him back-to-back hat-tricks at Celtic Park after scoring three against Dundee United last month.

McDonald, nursing the match ball, insisted that he had no qualms about sitting out the game in the Stadium of Light but admitted he is confident of scoring in every game he plays in, especially at Celtic Park.

He said: "The manager wanted a more physical presence in Portugal.

"You can't play every game and I support every decision the manager makes, he knows better than me.

"And whether I play or not, I am supportive of the team.

"We were unlucky to get beaten in Lisbon, we were only four minutes away from getting a draw and if that had happened people would have said he got his tactics spot on.

"But I always think I am going to score if I am playing.

"We have so many good players and make so many chances that I don't need to go searching, I can poach."

Motherwell manager Mark McGhee insists the loss of the first goal three minutes before the interval signalled the beginning of the end for his side.

He said: "We could have easily been ahead in the first half, we were in behind them five times and didn't make enough of it but we needed to score first.

"I don't think the outcome was ever in any doubt after they scored their first goal so close to half-time.

"Our Achilles heel is crosses into the box. I feel we are always going to lose a goal from corner and eventually we did and that took the pressure off them.

"That would have changed Gordon's attitude at half-time and from that point on, when you are chasing a goal against a renewed Celtic at home, you are on to a loser.

"We are not big enough or aggressive enough in both boxes. It's not rocket science."

McGhee has injury concerns for their CIS Cup tie against Rangers in midweek.

Stephen Hughes, Paul Quinn and Jim Paterson were all replaced and McGhee said: "Paul is recovering from a virus and he was exhausted so we didn't want to hurt him.

"Stephen has a hamstring injury and is certain to be out but Jim has a chance."