SOUTHAMPTON, England, Sept 14 (Reuters) - New signing Matthijs de Ligt grabbed his first goal for Manchester United ( MANU ) while Marcus Rashford scored for the first time since March in a 3-0 Premier League victory at Southampton on Saturday after a shaky start to the season.

Alejandro Garnacho added a late goal for Erik ten Hag's side who started the day 14th in the standings after back-to-back losses. They now have six points from four matches while newly promoted Southampton remain without a point.

Southampton dominated early on but squandered a chance to take the lead in the 34th minute after United goalkeeper Andre Onana saved Cameron Archer's poor penalty, sparking an immediate shift in momentum at St Mary's Stadium.

A minute later, De Ligt headed in a sumptuous ball from Bruno Fernandes. Rashford, who had gone 13 games without a goal, then ended his drought with a diagonal shot from outside the 18-yard-box to the far corner in the 45th. The hosts were reduced to 10 men in the 79th minute when defender Jack Stephens was sent off for a high tackle on Garnacho.