Former Celtic midfielder Vidar Riseth has warned the current Parkhead squad they had better do as Ronny Deila says if he is named their new boss - or they will find themselves looking for a new club.
Ex-Norway international Riseth spent six months at Deila's Stromsgodset outfit towards the end of his playing career and knows just how the Hoops' new number one target operates.
Riseth was a veteran approaching his 40s while Deila was a fresh-faced 33-year-old just a year into his first coaching post.
But Riseth, who spent two years with the Glasgow giants and landed a League Cup winners' medal in 2000, was impressed with his dedication to attacking football.
However, he has cautioned the Parkhead players Deila is in line to take charge of that the 38-year-old will not tolerate anyone who does not accept his tough methods.
Riseth said: "Ronny was my coach for six months at Stromsgodset. At the time he was 33 and I was 38.
"But even though he was quite young at that point, he was really, really tough and wanted all the players to work hard on the training pitch and in matches.
"He's tough but fair and always has a good relationship with the players. If they are not playing, he will tell them why.
"But if they don't work the way he wants them to, he will sell them. It's as simple as that."
Delia led Norwegian minnows Stromsgodset to their first league title in 42 years last season and has now replaced ex-West Brom boss Steve Clarke as the man Celtic want to replace Neil Lennon.
But Riseth, 42, insists his former boss is strong enough to make the switch from working in front of a few thousand fans at his current club to managing Celtic in front of a sold-out Parkhead.
"At Stromsgodset, they play in front of less than 10,000 supporters for every game, but I have seen him take his side to Rosenborg where there are 20,000 shouting at him and it never phases him," said Riseth, who also played for 1860 Munich, Rosenborg and Lillestrom before retiring in 2010.
"He is really strong in the head and that will help him if he goes to Celtic.
"The Celtic fans won't know much about him but in Norway, he is a big, big name.
"He won the league in Norway with Stromsgodset last year with just 10 per cent of the budget that Rosenborg could spend.
"With the style of football he plays, he will soon make himself a hero to the Celtic supporters.
"If he can get the team to play the way he wants them, the club's potential will go sky high. He is the man to build the club's future."
Celtic have seen attempts to land a box-office appointment rebuffed after talks with former Parkhead icon Henrik Larsson and Republic or Ireland assistant boss Roy Keane collapsed.
But Riseth is convinced Deila would do a better job, saying: "I know a lot about Roy Keane as a player but he hasn't done so much as a coach.
"As for Henrik, he is a good coach and has done well in Sweden but from all the coaches working in Norway, Sweden and Denmark, Ronny is at the top."
Stromsgodset have gone 46 games since their last home defeat in June 2011 and Riseth has told the Hoops supporters they will be in for a treat if Deila is given the nod by the Parkhead board.
"Ronnie is a really offensive coach," he said. "I've been over to see Celtic a lot over the last couple of years and they did well. But I think the fans will see a big difference in just how offensive the team will be if Ronny gets the job.
"He likes to get the full-backs pushing up and to get the ball moved up the pitch quickly. He will want the team to attack all the time.
"His team play a lot like Bayern Munich with the whole team joining in the attack.
"Right now, he is the best coach in Scandinavia, 100 per cent."