Solskjaer told reporters on Tuesday: "The gaffer showed tremendous trust in the players we had last season. We hadn't won the league for three years and he only signed one player, Michael Carrick.
"This season he's bought a few new young players in -- probably to challenge the older ones as well because you can't live off your past glory at this club."
The 34-year-old Norwegian, who is on his way back from a knee injury, believes the likes of Nani and Anderson will have to adjust to Premier League football.
"The young players are going to need time to settle in England, but the way we've nurtured Wayne and Cristiano, who came to the club as really young, talented players, the gaffer has made them into top world players.
"That's what you get at Manchester United, you get the challenge every day in training. They have to have that desire to improve all the time."