Messi scored two early goals to help Barcelona beat United 3-0 on Tuesday and reach the Champions League semifinals for the first time in four seasons with a 4-0 aggregate score. The Dutch International said "I don't know, we'll see".
United have lost three of their last five matches since the permanent appointment of the Norwegian, with their other two results being lethargic and unconvincing wins over West Ham and Watford in the league.
Liverpool, who take a 2-0 lead to Porto on Wednesday, are now the most likely obstacle between them and their first Champions League final since they last won this tournament in 2015.
United, who started boldly and brightly against Barcelona, attacking and heeding the words of Johan Cruyff outside the stadium to "Go out and enjoy yourselves".
Solskjaer's most important work this offseason might simply be keeping Pogba at the club, especially if United does not qualify for the Champions League.
Weaknesses are not easy to find in this Barcelona side, but if there is one it is that most of their key players - Messi, Suarez, Pique, Busquets - are now the wrong side of 30 and they no longer play with the same zip as they used to.
The five-time Ballon d'Or victor was kept quiet in Barca's 1-0 win in Manchester last week but he was lethal on Tuesday - a pair of goals in the space of three minutes extinguishing United's hopes.
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After leading his side to victory, Messi was informed that Ronaldo and Juventus had crashed out and was asked about the Italian side's exit. Yesterday we saw who we will get in the Champions League semi-finals.
But Rivaldo, a former Barcelona player, wasn't happy with the way Coutinho celebrated his goal and suggested it may further anger Barcelona fans.
Coutinho linked up with his former Liverpool FC team-mate Luis Suarez and Argentina worldwide Lionel Messi at Camp Nou.
Once their rivals ran out of steam, Messi and Barca controlled the show and their rivals didn't have a scoring chance until injury time.
With Barca already well on the way to the last four by the 61st minute, Coutinho had nothing to lose when he unleased a majestic curling effort that raced into the top corner from 20 yards.
Manchester United are ready to hand Ole Gunnar Solskjaer a £250m transfer war chest as he looks to strengthen his squad this summer.