Martinez wary of Van Persie
The Netherlands international striker has scored four goals in three Premier League matches for the Red Devils since joining them from Arsenal last month.
Van Persie is likely to start against Wigan at Old Trafford on Saturday, and Martinez is aware of the 29-year-old's firepower.
"We all know what level Robin van Persie is at. What he did with Arsenal - not many players can reach that level," Martinez told The Wigan Observer.
"Obviously he went to Manchester United, and you're expecting him to take a little bit of time to settle in.
"But he proves everyone wrong with a phenomenal display against Southampton."
Wigan have picked up four points from their three Premier League games so far this season.
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