The Arsenal manager does not believe the Germany international can be expected to make a difference on his own, though says the 25-year-old's best years are ahead of him
The 25-year-old made an instant impact following his club-record move from Real Madrid in September, and has helped Arsenal to the top of the Premier League table.
However, recent unspectacular performances and a goal-drought that extends back to December 8 has seen the former Werder Bremen man criticised and his £42.5 million pricetag called into question.
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"Sometimes people expect him to make the difference alone," the Frenchman told the club's official website.
"Sometimes when it doesn't work you expect him to take the ball and put it in the net. He is more a passer than a finisher.
"(Goalscoring) is one of the things he can add to his game for sure. It doesn't need to be criticised, it needs to be encouraged.
"He is 25, he can only get better. The best years are coming for him now."
Arsenal confirmed on Monday that Wolfsburg assistant manager Andries Jonker will become the head of their academy in July, replacing the departing Liam Brady - news that has been welcomed by Wenger.
"I am very pleased that Andries is joining us," he added.
"He has a big reputation in the game and was a key part of the team which developed the structures which are now producing such strong young players in Holland.
"I look forward to working with him. I would also like to thank Liam for his work which has been outstanding over many years."