United dominated in the first-half without ever hitting top gear against an efficient Villarreal.
At only seven minutes, Rio ferdinand wasted an opportunity to put United ahead, but he was surprised when Owen Hargreaves' corner arrives at his feet and he miscued his efforts off target.
Villarreal keeper Diego Lopez looked uncertain, and he was called into action to save efforts from Nani and Carlos Tevez.
United deserved a clear penalty before the interval when Ji-Sung Park was tumbled by Joan Capdevilla, but German Referee Wolfgang Stark waved away the appeals.
United pressed until the end, but Villarreal held on to frustate the holders.
Sir. Alex Ferguson said: "Ronaldo has had a turbulent summer and a lot has been said about it, but when I had my meeting in June in Portugal with him that was over. He dedicated himself to getting fit for the club. The Crowd's reception was important for Cristiano."
Van der Sar, Neville, Ferdinand, Evans, Evra, Nani, Hargreaves (Anderson 62), Fletcher, Park (Ronaldo 62), Rooney, Tevez (Giggs 81).
Subs not used: Foster, Brown, Vidic, O'Shea.
Ref: Wolfgang Stark (Germany)
Man of the Match: Ji-Sung Park
Source: BBC News
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