Celtic manager Ronny Deila heaped praise upon Stefan Johansen for a remarkable turnaround since his teenage days in the Norwegian leagues.
The 24-year-old midfielder, who played under Deila at Tippeligaen-winning Stromsgodset, claimed the SPFL Player of the Month award for February.
"It's unbelievable what he has achieved when we saw where he was when he came to Stromsgodset," said Deila.
"When he was 18, he had a reputation of bad attitude and wouldn't make it."
Johansen joined Stromsgodset in 2010 after breaking into the first team with Norwegian top-flight rivals Bodo/Glimt.
"We got him for free, just took a chance on him, and he came to Stromsgodset in a culture that was good and we got the best out of him," said Deila.
"He worked so hard in training every day, he was very humble and patient and that's important in the development of young players.
"In the end, after one-and-a-half years, he got into the team and the next year he was player of the year in Norway and went to Celtic.
"I think he learned the hard way how to work in the right direction and now we are starting to establish the same kind of environment and culture here. He is one of he leaders in that."
Deila took the reins at Celtic in June 2014 and Johansen has had a major hand in their recent success since following the manager to Glasgow five months earlier.
The team boss endured a trying start to the role, sustaining criticism in the early stages of the season as his side were knocked out of the Champions League by Maribor and dropped domestic points to Inverness Caledonian Thistle, Dundee, Motherwell and Hamilton Accies.
However, Celtic remain on course for a domestic treble, the fourth in the club's history, going into Sunday's League Cup final against Dundee United.
"I can see now how difficult it is," said Deila. "I understand why it's only been done three times in Celtic history.
"You get so many matches and it's pressure in every game, that's why it's so unique.
"But we have a chance and we're going to follow that dream.
"The League Cup is the first one we can get. The whole club, the whole team is hungry for silverware.
"I think, if we play at our top level, Dundee United are going to struggle."
Deila admits it took time for "an unknown person from Norway" to win over the Celtic support.
"The hard part is done, but I will never be satisfied," added Deila.
"There is always something to improve and get better, but the finish is much easier, much more fun than the foundations."