The Red Devils are currently fourth in the table heading into Sunday’s crunch clash with Tottenham at Old Trafford, five points behind defending champions City and one behind third-placed Arsenal.
Van Gaal’s men saw their last realistic hope of winning a trophy this season ended by Arsenal last week as the Gunners beat United 2-1 in the FA Cup quarter-finals.
We can be second or third. It is not a big difference
Louis van Gaal
And the Dutchman now wants to see more consistency from his team in the final 10 games of the season as they look to secure a top-four finish.
“The coming matches are very decisive,” Van Gaal told a news conference on Friday.
“We are so close to a lot of clubs. We can be second or third. It is not a big difference, I believe.
“Manchester United have to be one of the teams who have to play in the Champions League.”
Van Gaal is also backing his United players to improve in the final few weeks of the season after failing to produce consistent performances this season.
“We have the confidence to reach the goal we set at the beginning of the season,” he continued.
“I have a lot of confidence in my players. From what I see in training sessions, we have progressed. But there is a big difference between training sessions and matches.
“We have to wait for the big victory. Then, maybe, we shall have more spirit and also more confidence to win our games.”
United still have to face the likes of Liverpool, Arsenal, Chelsea and Everton before the end of the Premier League season.
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