Adnan Januzaj marked his return to the starting XI with a 29th-minute winner on Friday as United moved to the top of the table, but Van Gaal was dismayed by the ease with which his team conceded possession.
Having mustered only one shot on target in their 1-0 win over Tottenham Hotspur last weekend, United found the target just twice against Villa, but it was wayward passes, rather than shots, that concerned Van Gaal.
“When you score more than your opponent, it's enough,” he said. “But I think you are right, because we had too many unnecessary ball losses.
“That was not only Adnan Januzaj, but also Memphis Depay and Wayne Rooney. So a lot of players. I can say more. We have to improve that.
“But in spite of this, we had more chances than the opposition, and bigger chances, and we scored a fantastic goal after a fantastic pass from Juan Mata and a fantastic cut from Adnan.”
Januzaj's goal saw him race onto a splendid pass from Juan Mata before cutting inside Villa captain Micah Richards and beating Brad Guzan with the help of a deflection off Ciaran Clark.
Januzaj was replaced by Ander Herrera on the hour and while Van Gaal said the substitution had been pre-planned, he was critical of the Belgian's use of the ball.
“I'm pleased with the goal, because it was a wonderful goal, how Adnan scored, but you have to do more than only scoring a goal,” said the Dutchman. “That was less good than the goal.”
Asked if Januzaj had lost the ball too much for his liking, Van Gaal replied: “Yes.”
Januzaj has been linked with a loan move to Sunderland, but while he said he intended to stay at Old Trafford and fight for his place - dismissing the speculation linking him to the Stadium of Light as “just rumours” -- Van Gaal was coy when asked if the winger would be loaned out.
“You have to wait and see until we close the transfer period,” he said. “That's now my benefit of this transfer period.”
Van Gaal refused to be drawn on David de Gea's future after the Spanish goalkeeper, strongly linked with Real Madrid, was again left out in favour of Sergio Romero.
And while he said United would go into Tuesday's Champions League play-off first leg at home to Club Brugge with confidence, he warned that his side would need a defensive performance of similar fortitude to those produced against Villa and Spurs.
“When you win two times then you shall have a lot of confidence, but every match is difficult,” he said.
“Belgian teams can play very compact and can defend and always a team has a chance. When they score out of that chance, it shall be very difficult.”
Villa manager Tim Sherwood gave home debuts to six players and with four of them taking their first steps in the Premier League, he conceded that it will take time for his team to find a winning formula.
“The players are still acclimatising to England, let alone the football, but it's going to take time,” he said.
“We expected that. But they give me everything and they try and take instruction on. It's not perfect, but they will improve.
“The idea is to get them on the training field and hope they can gel.”
Villa might have had a penalty shortly before half-time when United right-back Matteo Darmian appeared to grapple with Richards, but Sherwood was sanguine about referee Mike Dean's decision to wave play on.
“You can get them. Sometimes you do, sometimes you don't,” he said.
“I won't be sticking pins in the referee. We didn't get it, got a deflection on the goal. Someone wasn't shining on us.” – AFP
Original source: Van Gaal unhappy with sloppy United