United were clinical at Old Trafford on Monday night as Stoke - under the watchful eye of new manager Paul Lambert in the stands - passed up some presentable chances against Jose Mourinho's men.
The Old Trafford crowd will also have been relieved to see Martial starting and scoring given recent transfer speculation linking him to Arsenal as a possible makeweight for Alexis Sanchez, though Mourinho hinted that Henrikh Mkhitaryan's absence from the matchday squad could see the playmaker leaving this month.
Valencia got the ball rolling as the Ecuadorian used his return from injury to score a stunner with his weaker foot soon after kick-off.
The 32-year-old - who primarily uses his left leg purely for support - received a Paul Pogba pass, cut inside from the right flank and unleashed a vicious effort which curled into the top right-hand corner of Jack Butland's net after nine minutes.
But despite a strong start, United were lucky not to be pegged back level as Stoke wasted a host of presentable chances.
Stephen Ireland twice missed when well placed around the penalty spot, while David De Gea lost the flight of a cross under pressure and could only watch as Eric Maxim Choupo-Moting's half-volley deflected wide of an empty net.
But the Potters were made to pay for those missed chances as Martial all but ended speculation of a potential move to Arsenal as he curled home a fine second eight minutes from the interval after being teed up by Pogba.
Xherdan Shaqiri went close for Stoke on the stroke of half-time, but De Gea was equal to the Swiss forward's low effort with a strong left hand.
Stoke opened up as they went in search of a route back into the contest, though Martial and Juan Mata passed up chances to add to United's lead around the hour mark.
But Lukaku got the goal his performance deserved with 19 minutes left of the clock as the Belgian held up a Martial pass into the box on his chest before finding space to finish low into the bottom right-hand corner.
While Pep Guardiola's City still hold a double-digit points advantage over United, the Red Devils at least took advantage of the chance to add a little spark into the title race.