Hearts last night launched an investigation after Gordon Strachan was verbally abused in a Tynecastle corridor by a supporter.

Hearts last night launched an investigation after Gordon Strachan was verbally abused in a Tynecastle corridor by a supporter.

The Celtic manager had been discussing his side's 2-0 victory outside the media room when a man passed and called Strachan an "a*******".

The supporter, who had come from a hospitality area, then headed straight for an exit. A Hearts spokesman said: "An investigation into the incident has already begun. Once the individual has been identified, appropriate action will be taken."

It was the only difficult moment of the afternoon for Strachan who watched his side cruise to victory after early goals from Shaun Maloney and Gary Caldwell.

"We started in top gear," said Strachan. "We started with a determination to win. We got the goals and felt comfortable in the game, apart from set plays as it is the land of the giants here."

The Celtic manager said the victory was the product of "hard work". He admitted Celtic "came down a couple of gears" after Marius Zaliukas was sent off for a foul on Scott McDonald, an offence that was also punished by a penalty missed by Paul Hartley.

The Celtic manager immediately looked forward to the Group E match with Manchester United at Parkhead on Wednesday night. "We have to play against the best team in the world," he said, emphasising the size of the challenge by referring to United's recent 10 combined goals against West Bromwich Albion, West Ham United and Hull City.

"Spirit and determination are not a problem. But we need breaks against Manchester United. If we are to do well, we need a break," he said.

"We need to be at our best. In terms of motivation and character, we will be fine. But we will not have the same ability as them. You know that and I know that. That is the best team in the world.

"Manchester United are by far better than France and Italy. That is the competition we are playing against. It is unbelievable what they can do to teams."

Strachan revealed that Shunsuke Nakamura, rested for yesterday's game, would be available against United.

However, Celtic will still be without the physical bulk of Jan Vennegoor of Hesselink and Georgios Samaras up front. Barry Robson, Celtic's man-of-the-match yesterday, will be available, though, and made a strong case for inclusion.

"We know how hard it is going to be," Robson said. "We know they are a good side but we are a good side, too. We are in front of great fans in a massive stadium. We need to try to put on a show for our fans and for ourselves. We have done it before against United."

Robson promised Celtic players "would get right in their faces" right from the start, adding: "We have some good players too and they can hurt United. With the fans behind us, we have a chance."

Celtic, meanwhile, have been linked with Silvinho, the Brazilian left-back at Barcelona. But Strachan would only say last night: "I have not been involved in anything yet."

Csaba Laszlo, the Hearts manager, blamed the loss of two early goals for his side's capitulation. He emphasised Hearts must stop giving teams a goal start at the beginning of games.