Manchester United want to address three problem positions by signing Aaron Wan-Bissaka, Kalidou Koulibaly and Ivan Rakitic in the summer transfer window.
With 36 goals conceded so far, the Red Devils have let in more goals this season than the whole of last and interim manager Ole Gunnar Solskjaer knows the team have to strengthen defensively if they want to challenge for the Premier League title next season - regardless of whether he gets the job on a full-time basis.
Current center backs Chris Smalling and Phil Jones recently signed new contracts but have had spells on the sidelines and doubts remain over their ability at the highest level. First choice right back Ashley Young is 33, so next year could be his last at Old Trafford.
Wan-Bissaka, 21, has enjoyed a great season at Crystal Palace, playing 25 games and providing one assist, while United have a longstanding interest in Koulibaly - they reportedly had a £95m bid rejected for him last month.
The middle of the park is another area of concern for United, especially if first choice trio Paul Pogba, Ander Herrera and Nemanja Matic get injured.
United have been hit with as many as ten injuries in the past few weeks, meaning Solskjaer has had to play inexperienced duo Scott McTominay and Andreas Pereira while youth prospect James Garner made his debut in the 3-1 win at Selhurst Park on Wednesday.
Ivan Rakitic has enjoyed a trophy-laden career at Barcelona and would add class to United's midfield. The 2018 World Cup runner up was linked to Inter in January, ultimately staying at Camp Nou, but a move to the Premier League could tempt him away.