Ole Gunnar Solskjaer extended his winning start at Manchester United to eight games in all competitions, as Brighton was defeated 2-1 at Old Trafford.
The hosts received a blow before the fight when Luke Shaw came out of the disease and was replaced in the XI by Diogo Dalot.
United took the lead in the 27th minute from the penalty spot, and Paul Pogba converted after receiving a foul from Gaetan Bong.
Ten minutes later, Anthony Martial almost added a second after Victor Lindelof overcame the ball, but Brighton goalkeeper David Button denied it.
But, three minutes before half-time, Marcus Rashford scored his fifth goal in his six Premier League games since Solskjaer took over, but he made sure points for United.
In his 150th appearance for the club, the 21-year-old curled up in the top corner from a close angle.
Gross reduced the blue's arrears in the 72nd minute, drilling in a short-range shot from the bottom of the bar after Davy Propper floated on a perfect one-inch cross with the outside of his foot.
United, who missed several opportunities to increase their advantage at the opening hour, was forced to hold out in the final stages when the visitors threw a flurry of crosses into the penalty area.