Runaway leaders Manchester City hold a 13-point advantage, having played one game fewer than the rest of the top five, leaving United, Chelsea, Tottenham Hotspur and Liverpool to battle it out to be the best of the rest.
"It stays the same, it is tough," Courtois told the club's website.
"City are obviously far away but for the second, third and fourth spot there are five teams so it will be hard until the last match of the season.
"But I think we have enough quality as we saw on Sunday and we showed it against Barcelona. I think we are a very good team but there are some other good teams around us as well."
Chelsea now face crucial fixtures against City and Crystal Palace as they look to regain their footing in the league, after three defeats in their last five matches.
The reigning league champions travel to Barcelona for the second leg of their last-16 tie on March 14.
(Reporting by Aditi Prakash in Bengaluru)
