MANCHESTER (Reuters) – Ruud van Nistelrooy could miss Manchester United’s Champions League clash against Olympiakos today because of a persistent hamstring problem, manager Alex Ferguson said yesterday. «Ruud van Nistelrooy is quite doubtful,» Ferguson told a news conference. «We took a risk and played him on Saturday, but with hamstrings, if you don’t clear it up, it goes on and on and on and we will give a lot of consideration to that (today).» In van Nistelrooy’s absence, Paul Scholes would probably play in attack alongside Ole Gunnar Solskjaer. Fit-again duo Mikael Silvestre and Juan Sebastian Veron have been added to the squad, while England defender Gary Neville is a confirmed starter. United’s task at Old Trafford looks simple on paper due to Olympiakos’s poor away record. They have drawn one and lost seven of their last eight away games in Europe, and lost 3-0 at Old Trafford in the Champions League last year. But Ferguson is aware of the number of shocks in Europe this season and has warned his team against underestimating the Greeks. «The surprise was Olympiakos losing to Maccabi Haifa,» Ferguson said. «That was a shock. Nobody expected that… I have seen some of the video of the game and I don’t think it was a 3-0 score line. But the striker of Maccabi Haifa (Yakubu Ayegbeni) did very well. He was a real threat and sometimes that can happen. One player can make a difference and he did that in that game.» «I expect a tough game. (Olympiakos) have a lot of experience there with Giovanni and Christian Karembeu and we have to respect that. They showed last year they have good quality and we have to concentrate.» Ferguson said victory over the Greeks would almost certainly confirm United’s place in the next stage of the competition. United top group F with a maximum six points while Maccabi and Olympiakos have three. Last year’s Champions League finalists, Bayer Leverkusen, are bottom of the group with no points.