Recently-appointed football director John Murtough reportedly began work on summer deals the day after United’s Europa League final defeat in Gdansk.
While winger Jadon Sancho has resurfaced a the top target, right-back Trippier has also re-emerged on their radar.
The Red Devils looked into his transfer in January, but pulled the plug due to his off-field suspension.
However, manager Ole Gunnar Solskjaer reportedly has concerns about Aaron Wan-Bissaka. As such, he wants to bring in Trippier to act as solid competition.
According to Football Insider, United have now submitted an opening bid worth around £10million. However, they have faced rejection from the La Liga champions.
Indeed, Atletico have told United chiefs to increase the offer if they are to prise the England international away.
In any case, the 30-year-old is supposedly a ‘priority’ target and so United could come back in with a better bid.
As for Wan-Bissaka, Solskjaer wants to try his current right-back in a more central role in pre-season this summer. That could be on the right of a three-man defence, or as a centre-back in a back four.