Manchester City assured themselves of direct entry into next season's Champions League group stage on Sunday as Arsenal stayed on course for a top-three finish as well. City won 4-2 away to Swansea before third-placed Arsenal moved two points clear of Manchester United after coming from behind to earn a 1-1 draw at Old Trafford.
Ander Herrera's volley gave United, fourth in the table, the lead on the half-hour mark.
But the Gunners equalised eight minutes from time when Theo Walcott's cross diverted off defender Tyler Blackett and, with David de Gea off injured, past wrong-footed substitute goalkeeper Victor Valdes, who was making his United debut.
Only the top three sides in England at the end of the season - which include already crowned champions Chelsea and City - are guaranteed a place in the group stage of European football's elite club competition, with the Premier League's fourth-placed team having to enter a qualifying round instead. United now have it all to do to overtake Arsenal.
The Gunners, who have a superior goal difference, can take six points from their remaining two matches, at home to Sunderland and West Bromwich Albion on Wednesday and Sunday respectively, while only three are available to United when they travel to Hull on the final day of the season next weekend.
Earlier, three goals came before half-time at the Liberty Stadium.
Yaya Toure, assisted by an error from Swansea goalkeeper Lukasz Fabianksi, and James Milner put Manchester City 2-0 up before Gylfi Sigurdsson pulled a goal back for Swansea on the stroke of half-time.