Striker Osman Sow is more of a team player than he was when Robbie Neilson first worked with him.
The 27-year-old played under the Dons boss at Hearts for two years before securing a move to the Chinese Super League with Dacia Chișinău.
And after spending 18 months in the Far East, Neilson believes Sow is a more-rounded player than he was when he left for China.
"I've seen a big change in him in training already, in the 18 months we've been apart," said the manager. "He left and was a great boy, but he looked after himself really. Now he's come back and he's more of a team player, more a leader of the team as well."
Sow played an hour of his debut against Gillingham last weekend, scoring the only goal of the game in Dons' 1-0 win. But he was left out of the side which lost 4-1 to Swansea City on Tuesday night, with Neilson opting to rest most of his regular starters for the Carabao Cup clash.
And until Sow fully acclimatises and gets used to being back in Britain, Neilson warns fans not to expect too much from him immediately.
Neilson said: "It will be four or five games until he's really at it, but you can already see his quality - his pace and ability.
"He was over in China and the Emirates and the pace there is very, very low so it will take him a bit of time to get up to the pace of it.
"Osman flew back from China last week, he then trained with us for a few days and then started on Saturday, but we were very wary of doing it.
"(On Tuesday), it wasn't worth the risk. He's going ot be one of our key players this season, so with this workload without a pre-season in a short space of time is just too much for him."