John Hartson was a popular player at Celtic from 2001-06, winning three league titles, the Scottish Cup twice and a Scottish League Cup.

But, as he told the BBC's Sacked in the Morning podcast, the Wales striker was not always on the right side of the manager who signed him, Martin O'Neill.

The last trophy won at Celtic on O'Neill's watch was the 2005 Scottish Cup and Hartson played a significant role in helping the holders overcome Heart of Midlothian in the semi-final with an assist for Craig Bellamy's winner.

"I've made the goal," he explained. "I've won us the game almost, you know? And then I look over, the referee blew the whistle. I looked over. Number 10. My number. I can't believe this. He's bringing me off.

"Whenever Martin O'Neill brought a player off, he liked that player to go and sit on the bench and accept a jacket and sit next to him, shake his hand on the way off.

"I thought, I'm going straight down the tunnel, you know? Stevie Walford, one of Martin's assistant coaches, threw the jacket at me and I threw it back.

"I walked in the dressing room and there was like sandwiches and bottles of water and pots of tea - and I just threw the sandwiches, threw everything.

"Henrik Larsson had a bit of tomato ketchup on his shirt and all that. Chris Sutton had new shoes. He had some tuna on his brogues. And then the boys won the game."

The game finished 2-1 and Hartson explained the post-match scene in the dressing room.

"After the game, all the lads are delighted," he continued. "We've got into a Scottish Cup final. Really tough game. It was windy, the pitch wasn't great.

"I'm just sitting there like a spoiled kid, still disappointed with coming off you know? It's all, 'well done, lads, great finish and all'. We're in a final, in something to look forward to at the end of May.

"Martin has gone, 'John', the room's just gone silent. 'What's the matter with you'? And I said, 'look', I said, 'why did you bring me off'? He said, 'look son, every now and again', he said, 'you've got to run around a little bit. And in the 72nd minute, John, you just weren't moving. So I brought you off."

O'Neill's assistant John Robertson was in close proximity.

"Martin's come towards me and I've stood up," Hartson recalled. "There was never, ever going to be a reaction from me, a physical reaction. He said to John not to sort of hold him back, Martin says that, but from my point of view, nothing was going to happen.

"I stood up just to, like almost, you know, overpower him. There was a sense of, because of that, the whole night became subdued. I spoiled the night. Typical, behaving completely like a spoiled brat.

"And managers I always feel now, even though I played for loads of managers, I always feel the manager is always right. Whatever decision the manager makes. Looking back, I think he was right."

Of course, Hartson's storied career also included a spell at Arsenal and 51 international appearances.

And, during Arsenal's Highbury days, he experienced the culture shock of Arsene Wenger's arrival.

"He came in and changed literally everything," Hartson said. "Changed the food, the diet. 'Eat slow' he would say to the players. And we would do a long run in the morning, about 20, 25 minutes we would jog around the training ground, get the lactic acid out of your legs before you started going.

"Every day after training we'd go back inside, Arsene Wenger would stand in the middle and we'd all form a circle. He'd go from his feet to his knees to his hips to his shoulders. We'd all have to stretch, stretching was massive. Before he came it was, 'let's go... liquid lunch'.

"To this day, Tony Adams, Ray Parlour, some of the older boys, Ian Wright, Paul Merson, David Seaman… they would all say Arsene put a couple of years on their careers. And they were all big earners, so he would've put a couple of million on their careers."

Hartson left Arsenal for Harry Redknapp's West Ham in 1997.

"He was a wonderful manager, he was great with me, he wanted me to stay, he wanted me to sign a new deal," Hartson added of Wenger.

"But I had honest Harry, King of the Jungle, on the phone desperate to take me to West Ham. Desperate. He offered me the world. I left Arsenal. Then they did the Invincible season. So that was a good decision wasn’t it!"