Morrison left Old Trafford in 2012 to join West Ham United, before moving to QPR on loan earlier this year, but Simpson believes that his teammate has shown that he possesses the ability to still be competing for a spot in the United team.
"For whatever reason, it didn't work out at Man United. For me, he could have still been playing there now in the first team with the likes of Januzaj and the rest of them," Simpson, who also came through the ranks at Old Trafford, told reporters.
"It's not worked out but I'm sure he'll get back at the top. He's moved away and grown up in the last few years.
"He's been top-class since he's come here and I think his performances have shown that he's still hungry and he's still as good as everyone knows he is."
Morrison and Simpson are both expected to play against Derby County in the Championship playoff final on Saturday.