Inside Gordon Strachan's brutal, zero-tolerance 'character days' Celtic training regime

Strachan spent four years at the Celtic managerial helm from 2005 to 2009. Caldwell signed for Celtic in 2006 and he readily admits Strachan took his career to extraordinary heights and levels he never thought he was capable of playing at.

The 40-year-old insists that Strachan's infamous 'character days' were not only 'horrendous' but at times his brutal training regime pushed players to breaking point.

It also signalled the death knell for some Celtic players who just couldn't cope with the physical and mental demands of being at one of the biggest clubs in Europe.

"Gordon's pre-season training sessions are famous throughout football," Caldwell said. "They take both your fitness and mentality to another level. They are horrendous.

"I go to the gym every day and it is nothing like what Gordon put you through. He loves football, he loves coaching and a lot of it is with the ball and he is very open. But he had days that were called 'character days'.

"He said before we did it that it had nothing to do with fitness or running it was all about testing people's character. I have since spoken to him and asked why he would do those days?

READ MORE: Being Celtic's 'Victor Meldrew' and the moment it went wrong with Gordon Strachan - Derek Riordan Big Interview

"He said was testing his players very early and seeing who was going to be with him when the chips were down and he needed them and the players who wouldn't be at the football club moving forward.

"He actually said to me that some players on those character days he put the black mark beside their names and they were out of the club the following transfer window because, on those days, he had seen enough negative stuff that put him off.

"Gordon knew that in a crisis or difficult moments that every football team has then he couldn't rely on those players. He was very big on that, character and mentality were big things for him.

"There were a few famous character days. One I remember was the 33-minute run. We did it around Lennoxtown - the top two pitches. There were cones situated in a track-like manner and shape.

"Every 10 metres there was a cone and a player would start at each cone so every player was around the track 10 metres apart. Garry Pendrey, his assistant, was another fantastic man and great coach. He would start the whistle and that was your jog and on the next whistle, you had to sprint and chase the player in front of you and then on the next whistle you had to jog again. The team did that for 33 minutes solid.

"You didn't know how long the sprint was as you just had to run until you heard the next whistle. It was mentally hard. You had somebody chasing you and you had to chase the person in front and then the manager would be in the middle pushing you on to catch the player in front of you.

"There was a funny moment as you could not pass a player on the jog and as I was coming round halfway through Evander Sno cut the corner on the jog and passed me. When you are tired you can get a bit irritable so I had a go at him. The masseurs were in the corner laughing at me.

"On the next whistle, I tried to chase him but he was as quick as he wanted to be so he just ran away from me and I didn't catch him. I didn't catch him until the end and I told him he couldn't cut corners.

"Character days like that pushed every player to breaking point. He didn't do it to test your fitness, even though you would get fitter, it was mainly to see who would fold or break when things got really difficult.

"Training every day in Gordon Strachan's Celtic team was full pelt and no quarter was asked or given. There would be fights and cuts and bruises - it was proper hammer and tongs stuff.

"Gordon created that and instilled that and I think that is what made Celtic such a good team as we trained at 100 per cent and we could go into games ready to perform and replicate what we did at training and every week was a challenge."

Although Caldwell joked that not all of Strachan's notorious training sessions turned to gold after Celtic were defeated in the Champions League by Benfica when the manager indulged in a spot of mind games after the Portuguese outfit sent their club spies to run the rule over their opponents.

READ MORE: Neil Lennon's Celtic power play, Gordon Strachan's cutting one-liners and career 'barriers' from crossing Glasgow divide - Steven Pressley Big Interview

Caldwell said: "Gordon once ran us the night before a Champions League game against Benfica as he heard the coaches were in the stand watching us.

"We did no tactical stuff we just ran. Gordon wanted to intimidate them by showing Benfica we were a really fit team. It did not have the desired effect as we were a knackered team and we lost the match."

However, Caldwell - who was recently relieved of his duties as assistant to Shaun Maloney at Hibernian - said that Strachan remains his go-to guy in terms of football coaching and management.

Caldwell said: "Gordon was a massive influence on my career. He saw something in me and gave me the confidence to play for Celtic which is a demanding football club, he also helped me play in the Champions League as well as move on and play in the English Premier League.

"Since I left Celtic, he is still one of the first people that I would phone for some coaching or management advice.

"I like to meet up with him for a game of golf every now and then. He is somebody that made me see the potential that I had and dragged that potential out of me.

"Shaun (Maloney) and I spoke about that at Hibs every day in terms of trying to get more out of players. Gordon was brilliant at dragging that potential out of players and pushing you to places that you didn't think you could go. I will always be thankful for what he did for me."