United host Barca tomorrow in the first-leg of their Champions League quarterfinal.
"[Messi's] a fantastic player and he will go down in history as one of best ever," said Solskjaer.
"He will be difficult to stop but it's never impossible; it's not like it's Messi against Manchester United.
"[They have Luis] Suarez, [Philippe] Coutinho, [Arturo] Vidal - so many good players, so we can't focus on one individual. We have to focus on their eleven players."
The Norwegian did not reveal his plan to stop Messi, if he has one, and instead emphasised that the Red Devils' defenders will need to perform well.
"What kind of plan can you have to stop one of the best players in the world?" responded Solskjaer.