Manchester United boss Sir Alex Ferguson had a scout posted for Borussia Dortmund's victory over Champions League opponents Real Madrid this week.
Top of the agenda for Fergie was Robert Lewandowski, who struck all four goals in BVB's 4-1 rout.
The Daily Mail says United also took the chance to run the rule over Dortmund centre back Mats Hummels and Real midfielder Luka Modric on Wednesday night.