Strachan takes his men to face Manchester United on match day three

Celtic manager Gordon Strachan admitted that the defeat away to Villarreal makes qualification for the Champions League last 16 a tall order.

However, Strachan added that he was more pleased than ever with how his side had performed on their travels.

"We've got a mountain to climb now, but I would say we've proved we can play at this level," said Strachan.

"And for the first time away from home I sat back and thought I was happy with what I was seeing."

The 1-0 defeat leaves Celtic in third place in Group E after two matches, three points adrift of Manchester United and Villarreal.

Strachan admitted the set-piece goal that undid his side came from a wonderful player in Villarreal captain Marcos Senna.

But the Celtic manager thought the free-kick awarded when Paul Hartley was adjudged to have fouled Joseba Llorente was dubious.

"I've had a look at it and I'm not convinced it was free-kick," said Strachan.

"Only the player who was involved with it will know whether he dived or not, but the pictures themselves tell you.

"But in Senna they have a world-class player, simple as that, and once they went 1-0 up they showed what a really good team they are."

Despite the reverse Strachan says his side showed a new dimension to their play in European competition.

"Tonight we worried them when we had the ball, whereas in the past we didn't really look threatening away from home," said Strachan.

"I asked the players to perform and I don't think anyone would disagree that for 55 minutes we were excellent and reasonably comfortable at the back.

"After that, whether by design or coincidence, they started to work our areas of the pitch.

"But that performance is alright, that's good enough to win games in most places in the Champions League.

"It's just unfortunate we came up against one of the best teams in Europe at the present moment."