Goalkeeping legend Peter Shilton believes David de Gea is facing the acid test of his Manchester United career.

Shilton watched De Gea's early performances following his £18million move from Atletico Madrid last summer through splayed fingers. As the mistakes mounted, it became increasingly obvious De Gea was not up to the task of filling the vacancy created by Edwin van der Sar's retirement.

After conceding four times at Old Trafford last weekend, the former England keeper feels De Gea has to answer some pretty significant questions. He said: "It is possibly the biggest game of his career, and if he can come through it and have a good game, it could clinch the title for United and cement his progress. This derby is the acid test now."

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