Manchester United manager Jose Mourinho is targeting Chelsea midfielder Willian as part of his summer rebuilding plans at Old Trafford, sources have told ESPN FC.

Mourinho wants to add at least four new signings to his Old Trafford squad ahead of the 2017-18 campaign, with the United boss identifying the need for reinforcements at centre-back and in midfield, as well as aiming to sign two forwards to replace the injured Zlatan Ibrahimovic and Wayne Rooney, who is expected to leave the club at the end of this campaign.

Despite scoring 10 goals in all competitions for Chelsea this season, including two in Saturday's 4-2 FA Cup semifinal victory over Premier League title rivals Tottenham Hotspur, Willian has struggled to secure a regular position under Antonio Conte, starting just 13 Premier League games under the Italian coach.

The Brazil international was back on the substitutes' bench for Tuesday's 4-2 Premier League win against Southampton at Stamford Bridge, playing only the final 60 seconds as a late replacement for Eden Hazard.

Mourinho believes the 28-year-old's experience, pace and goal threat can add a new dimension to United's midfield next season and has instructed executive vice-chairman Ed Woodward to pursue the player, who he signed for Chelsea in a £32 million deal from Russian club Anzhi Makhachkala in August 2013.

Willian has struggled to hold down a place in the Chelsea team under Antonio Conte. Darren Walsh/Chelsea FC via Getty Images

Prising Willian from Chelsea will not be straightforward, however, due to the complications posed by the London club selling to one of their key rivals.

Chelsea rebuffed interest in Willian from the Chinese Super League in January and the club are in a strong position with the player after securing him to a new four-year contract last July.

But with Conte unable to find a regular starting spot for the former Shakhtar Donetsk midfielder this season, Mourinho is confident that United can exploit his lack of action and strike a deal with his old club for the player.