On Pellistri, Solskjaer told MUTV: "We feel that he has taken some good strides when he has been here and we looked at a few options.
"That was a good option. He felt comfortable and confident going there, so hopefully he will get some important match minutes in a good league."
Mengi will link up with United legend Wayne Rooney in his spell at Pride Park and Solskjaer believes his former teammate will have a positive effect on his development.
The United manager added: "When you get to that age sometimes it is not challenging enough, it doesn't prepare him enough for that physical striker for example that they might meet in the first-team. So to play in the Championship is a great challenge for Teden.
"That is going to be good for him. Wayne has been a top striker and I'm sure he will go in there and show him a few things himself."
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