to fitness with a bone-crunching challenge on George Thorne.
After being given some encouragement, the visitors improved following the interval with Brunt firing a fierce drive straight at David De Gea and Carrick clearing from McAuley from a dangerous free-kick to the far post. Brunt and Graham Dorrans also had efforts as United struggled to rediscover the flowing football that was a feature of the first period.
As the rain started to cascade down again, the match remained in the balance with Foster barely tested until clawing away a Valencia attempt seconds before Kagawa made way for top scorer van Persie. Clarke made a change of his own by introducing Chelsea loanee Romelu Lukaku to the action and the substitutions added punch to both attacks.
There was a let-off when McAuley almost atoned for his own goal by heading against the bar but referee Jon Moss rightly awarded a free-kick as the defender was climbing over Smalling to get to the corner. Nonetheless, it was another warning, if any was needed, that the high-flying Baggies were capable of getting something out of the encounter.
Sir Alex restructured the side in a bid to hold onto the lead with Valencia dropping to right-back and Smalling switching to the middle to form a five-man defence. It left United short of options going forward as the crowd became increasingly nervous, with this tension transmitting itself to the players.