The Reds Devils managed to pull off a transfer coup after Manchester United beat Premier League champions Chelsea to the signing of Romelu Lukaku.
The 20-time English champions signed the Belgium international in a £75m deal from Everton despite initial talk of the striker returning to Chelsea.
Lukaku scored 25 times in 36 games in the Premier League last season – only Tottenham Hotspur star Harry Kane scored more times than the Belgian star.
Questions have been raised about Lukaku’s big-game mentality following muted performances in Everton’s games against the so-called top five last season.
Birmingham manager Redknapp believes Manchester United will fancy their chances of challenging for the title but admitted doubts remain surrounding Lukaku.
“Jose Mourinho will be fancying his chances too at Old Trafford,” Redknapp told The Sun.
“Providing he gets the right stuff from Romelu Lukaku up front – and I have to say the big lad doesn’t always produce when you really want him to, United will be contenders.”
Lukaku scored 71 times in 133 appearances in all competitions during a three-season stay at Goodison Park after Chelsea sold the centre-forward to Lukaku in 2014.
The Belgian forward didn’t win any trophies during his spell at Everton but was part of the Chelsea squad that won the FA Cup in 2012.
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