After the full-time whistle is blown on United's match against Atletico Madrid in Oslo on Saturday afternoon, the Reds will be whisked on to a plane as they head back to familiar territory in Manchester where they'll kick off against the Spanish side 27 hours later. It is a fairly brutal end to pre-season preparations but the players should have expected nothing less from their new manager by now.
Ten Hag had specifically requested that his side play two games in as many days this weekend in a final bid to get as many players match-fit as possible. Despite the proximity of the two kick-off times, the belief is that the Dutchman will use rotation to ensure that as many players get a full 90 minutes as possible.
The match against Rayo Vallecano will come exactly a week ahead of United's opening Premier League match against Brighton on August 7, also at Old Trafford. The club are offering fans reduced-price tickets for the match against the La Liga team in a bid to create as close an atmosphere as possible to what can be expected next Sunday.
United fans may spot a few familiar faces in Vallecano's line-up. Two former Reds are their squad as both Bebe and Radamel Falcao are set to face their old club this weekend.
Here's all you need to know on the game.
Man Utd vs Rayo Vallecano kicks off at 16:00 BST on Sunday, July 31.
The game will be held at United's home ground, Old Trafford.