Manchester United boss Louis van Gaal says organised defending by Southampton made it hard for his players to create important goal-scoring opportunities.
The Red Devils failed to record a single shot on target against the Saints but the Dutchman believes his players gave everything in their attempt to break the deadlock.
The defeat brings United's 10-game unbeaten run to an abrupt end with Southampton moving up to third place in the table.
"We didn't create so many chances in spite of dominating the game," van Gaal told Sky Sports.
"Only the first minute, we gave them a chance but after that we have dominated the game without creating many chances.
"We create chances at the end, but we played with our heart. I put Fellaini at the top and then we made three big chances I think but was not enough.
"They were defending well. You have always got to take into account that the opponent can play well.
"They defended well, [they had] good organisation, but they came for a draw I think and they go away with a victory. That is disappointing. I think [Juan] Mata had three chances and he could make one of these chances, but okay, you cannot change the result anymore."
Luke Shaw and Angel Di Maria were second half substitutes but van Gaal was quick to say that the two suffered no fresh injuries during the match.
"Shaw was not injured but he needs match rhythm," the Dutchman explained.
"Also Di Maria, he is not injured but he needs match rhythm. That is why I had to change.
"Of course, we have players who are coming back but then we also need match rhythm. It is not so simple to play in the Premier League so I have to adapt to the circumstances."
