United sold the fullback to Bayer last week.
Solskjaer said, "We wish Tim all the best – six-and-a-half years I think he was here. He's an exciting talent and he's got the attributes, but he needs to play.
"When he gets regular game-time I think we'll see him for Holland and we'll see how good a player he is."
On United's transfer plans, he added: "There are opportunities that we can't really say no to and if it's the best for the club and the player then its something we look at. At the moment I can't update you on any of them, I don't really know where any negotiations are [up to]."