Manchester City have spent all season in second place but could drop down to fourth if Van Gaal's United and Arsenal both win today (Sat), 48 hours before their game at Crystal Palace.
United manager Van Gaal says a late title charge is still mathematically possible but says beating City and the Gunners to runners-up spot behind leaders Chelsea is a more realistic target.
If we can't finish first it's better to be second or third
Louis van Gaal
He said: "Mathematically we can still win the title but I cannot deny second place is more realistic because we have Manchester City to come at home and we have the strongest home record, so it's possible. We still have to play the top three so a lot can still happen.
"I would be pleased with fourth but I and my players want to be first. And if we can't finish first it's better to be second or third."
Finishing in the top three would mean United, who bid for a fifth successive Premier League win at home to Aston Villa today, avoid having to pre-qualify for the Champions League in August.