Marin a simple tap-in.
Marin, on loan from Chelsea, whistled another shot just wide and United were stung into action with Shinji Kagawa unable to collect a cute pass by Fabio. Büttner's deep cross beyond the back post was volleyed across by Valencia but Kagawa saw his header from the most inviting of positions somehow scrambled away by Beto on the line.
After going so close to reducing the deficit, it could easily have been worse for the Reds as Marin sped past Chris Smalling and saw his goalbound shot diverted onto the bar by De Gea's boot with five minutes of the first half remaining. Bacca blazed over when Diogo Figueiras was afforded far too much space on Sevilla's right before Valencia spurned the final opening before the break, lashing high and wide after Anderson picked him out inside the box.
United upped the tempo from the restart with Januzaj, now working hard in a lone striker's role, lifting over a curler from an Anderson pass. It proved only a taster of what the teenager is capable of as he played a key role in Valencia's goal. Collecting a pass from substitute Jesse Lingard, he forced a diving save out of Beto and latched onto the rebound, dribbling past Israel Puerto with ease to cross for Valencia to convert from a couple of yards out.
It proved to be the Ecuador winger's last contribution as manager Moyes made three substitutions but Januzaj and Lingard continued to impress, even if the latter, celebrating a first call-up to the England Under-21 squad after a successful tour, could not connect properly with a wicked Januzaj centre.
Büttner fired over as the hosts, by now, were creating the majority of the chances, and Lingard was inches away from meeting a Fabio pass in the middle when stretching with his right foot. A sustained spell of pressure came agonisingly close to yielding an equaliser when Wilfried Zaha was thwarted by Beto and Büttner had a low drive blocked following some spellbinding skill by Januzaj. Michael Carrick then tried his luck, only for Beto to again prove his worth with a smart save.