The Egyptian international took the Premiership by storm when he first joined Wigan on loan from Zamalek in the summer of 2008.

Zaki scored ten goals for the Latics during the league's first term. However, the 25-year-old hasn’t hit the net in any of his team's last eight games.

"When Zaki scored two goals at Liverpool in October, you'd have paid £20 million for him," Bruce was quoted as saying by the Telegraph.

"Unfortunately with the winter and the different climate, different training regimes, he's finding it tough at the minute."

Bruce added that Zaki can get back to his earlier dazzling form when the English climate gets warmer.

"Hopefully when the spring comes he'll come out of his shell again."

Zaki's goal drought has heavily affected Wigan's results, as the team managed just four goals in their last nine Premiership games.