Manchester United's dismal run of form continued as they were held to a 0-0 draw by Valencia in a drab Champions League clash at Old Trafford.
Valencia created the first threat after two minutes, Geoffrey Kondogbia playing Rodrigo into space before Eric Bailly got across, and United keeper David De Gea was off his line to intercept soon afterwards when a deflected Goncalo Guedes pass almost fell for Rodrigo.
Under-pressure United looked tentative but almost had a breakthrough thanks to Marcus Rashford, who won the ball back inside the Valencia area as Cristiano Piccini dawdled but was unable to find a teammate.
A 12th-minute Guedes shot brought a routine save from De Gea before Rashford tried to lift United again, cutting in but sending a low strike wide.
Forward came Valencia once more, Jose Gaya's cross eluding Michi Batshuayi and Guedes following up with a scuffed strike that posed no threat.
Piccini intercepted as Paul Pogba, anonymous in the opening stages, tried to play Rashford -- by far United's brightest player in the first 20 minutes -- in behind the visiting defence.
With United struggling to generate momentum, a subdued Old Trafford crowd roused themselves to get annoyed about a cynical challenge on Rashford by Francis Coquelin, who was booked.
Rashford then shot straight at keeper Neto from distance before having a header blocked when Antonio Valencia crossed.
Alexis Sanchez, back after his omission at West Ham, sent a tame free kick into the wall, and Rodrigo was booked after catching Bailly with an arm as the two contested a dropping ball.
With 10 minutes remaining until the break, Guedes, in acres of space down the left, cut in but shot ineffectively when he had teammates waiting for a pass.
Bailly was in discomfort after Rodrigo's challenge but was able to continue despite Victor Lindelof being readied to come on, but the first half was petering out with United posing few questions.
United appealed for handball against Ezequiel Garay when Luke Shaw crossed from the left, but the ball had hit his chest, and visiting captain Daniel Parejo was booked for pulling back Pogba.
Guedes cut in once again only to repeat his trick of firing over when he had other options, and at the start of the second half Romelu Lukaku tried to make his way down the left only to miscontrol.
United, who mustered only one effort on target before the break, were soon on the back foot as Guedes curled wide.
The home fans were becoming increasingly frustrated by United's laboured passing but almost had a goal to cheer when a loose ball dropped to Pogba after a Sanchez run and the France international's shot was bravely blocked.
Rashford saw a strike cannon to safety soon afterwards as Mourinho's side tried to up the tempo, but they continued to struggle to create clear openings.
As the hour mark approached, Chris Smalling met a Sanchez corner but could not generate enough power to test Neto, and soon afterwards Pogba had a free kick tipped over.
Rodrigo found Batshuayi, who shot too high, and with a little under 20 minutes remaining Lukaku's strike was saved as United readied Anthony Martial for the closing stages.
The France international replaced Sanchez, who again struggled to make an impression, and a Valencia change soon followed as Coquelin made way for Carlos Soler.
Guedes pulled a pass back towards Rodrigo, Antonio Valencia diverting the ball away, and nine minutes from the end another United free kick on the edge of the box, for a foul on Pogba, was blasted into the wall by Lukaku.
Russia international Denys Cheryshev came on for Guedes as Valencia made another switch, and the visitors threatened a late winner as Kondogbia's header across the area was scrambled clear.
Martial won a free kick near the byline to the left of the area after a foul by Piccini, who was booked, and Rashford's dipping effort from an acute angle clipped the top of the bar.
Lukaku and Gaya went into the book for fouls and the United striker then came close to a late breakthrough but, badly marked at a corner, could only steer his header over.
Kondogbia was booked for a foul on Nemanja Matic, giving United one last chance -- but after Fellaini had won a header his follow-up shot was deflected wide and boos greeted the final whistle on another uneasy night for Mourinho.