The Spain international has been in superb form in the 2017-18 Premier League season so far.
De Gea equalled a Premier League record with 14 saves during Manchester United’s 3-1 win at Arsenal at the start of December.
The 27-year-old was heavily linked with a move to La Liga giants Real Madrid over the past few seasons.
Indeed, the Manchester United number one was on the brink of a move to los Blancos in 2015 before a deal fell through on La Liga’s transfer deadline day.
De Gea has won Manchester United’s player of the year in three of the four past seasons under David Moyes and then Louis van Gaal.
Mourinho hasn’t been afraid to drop the Spain international for Sergio Romero in cup competitions and in some Premier League games.
Former Spurs forward Crooks believes Mourinho has played a big role in managing to keep De Gea at Manchester United.
“All credit to United. This is a player who was on the verge of signing for Real Madrid two years ago, and had it not been for a so-called ‘clerical’ error might have done,” Crooks told BBC Sport.
“One manager later, and Champions League qualification, we have not heard a squeak from De Gea about wanting to return to Spain or Real Madrid for that matter.
“I wonder how much of that is down to the presence of a certain Jose Mourinho?”
De Gea moved to Manchester United in a £18m deal from La Liga giants Atletico Madrid in the 2011 summer transfer window.
The Red Devils haven’t won the Premier League title since 2013 under Sir Alex Ferguson.
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