The hosts dominated the opening 45 minutes and Rickie Lambert put Southampton into a deserved first-half lead, with a Mata free-kick nine minutes after the interval enough to earn Ryan Giggs' side a point.
But, if the two clubs meet early next season, the chances are a number of the main protagonists may have moved on to pastures new.
With the managerial futures of both Giggs and Southampton counterpart Mauricio Pochettino unclear, it is possible two new coaches will be brought in over the summer - and for Saints their main challenge will be replacing a seemingly Liverpool-bound Adam Lallana.
The 26-year-old is reportedly the target of a big bid from Anfield and Lallana, who picked up both the club's fans' and the players' player of the year awards earlier in the week, once again showed how he can cut it against some of the best players in the league.
Giggs made seven changes from the midweek win over Hull for what will probably be his last match in charge as he recalled Nemanja Vidic for his final game.
But it proved to be a torrid outing for the man who will be lining up for Inter Milan next year as he and his defensive partner Rio Ferdinand, another who could well be departing Old Trafford, struggled to contain Southampton's rampant frontmen in the opening 45 minutes.
Nathaniel Clyne created the game's first chance as he crossed to Victor Wanyama who diverted the ball through to Lallana, but the Southampton captain could not steer a clever flick past David de Gea.
In front of the watching Roy Hodgson, Lallana then crossed for World Cup hopeful Luke Shaw but the left-back could only head onto the roof of De Gea's net.
Lallana was proving to be the main catalyst in the hosts' attack and, after profiting from a mistake from the unsteady Vidic, he bent in an effort that De Gea once again was able to gather, but it was not too long before another England international was celebrating putting Southampton ahead.
Vidic could only head a long ball into the path of Steven Davis under pressure from Lambert, who was then picked out to slot home his 13th league goal of the season.
United's players gathered around Mike Dean after the award of the goal as Vidic had a bloody nose after the clash with Lambert in the build-up to the goal.
Vidic's final game for United continued to go wrong as the Serbia defender was booked for hauling down Lallana after losing his own footing, with Lambert's tame free-kick held comfortably by De Gea.
The ever-busy Lallana came close to creating a second for Southampton with five minutes of the first half remaining but his flash across goal just eluded the head of the onrushing Davis.
Giggs reacted to a woeful first-half performance by replacing Shinji Kagawa with Michael Carrick and, after his side had started the second half on top, they soon drew level.
Danny Welbeck was bundled to the ground by Wanyama and Mata curled the resulting free-kick well out of the reach of Boruc.
The visitors almost took the lead moments later as Adnan Januzaj crossed unchallenged, with Welbeck only able to head over and, while Southampton continued to threaten, Vidic and Ferdinand were proving to be a much tougher nut to crack since the interval.
James Ward-Prowse replaced Lallana, with the Saints skipper receiving a standing ovation from the home fans in what could prove to be his swansong for the club.
Shaw, also linked with a potential departure after an impressive season, was the next to be afforded such an accolade as he made way for Calum Chambers with a little over 10 minutes remaining.
Those changes seemed to hand the impetus to United but, other than a late Welbeck chance, they could not muster a winning goal to potentially end the Giggs reign in style.