Hardest time of our careers this season, admits Andy Garner as Stags finally achieve safety, despite footballing lesson at Birmingham

But first team coach Andy Garner said it was still a great experience for Stags' patched-up side to play against such quality players at such an iconic stadium.

And he admitted it had been the toughest season in his and boss Nigel Clough's careers to keep Stags in League One for a second season in a row for the first time in 35 years.

First half goals from Keshi Anderson and Willum Willumsson put Birmingham in total charge at half-time.

Kieran Dowell added another just after half-time before Tomoki Iwata wrapped it up as Stags were sunk during a party atmosphere at St Andrews with the hosts celebrating lifting the League One title.

The comfortable win saw Birmingham beat the previous League One record points tally and left them a point behind Reading’s EFL record of 106 points with two games to play.

But Stags knew the result did not matter with their League One status having already been secured 24 hours earlier following defeat for Bristol Rovers against Reading.

“It was a tough afternoon but a good afternoon,” said Garner.

“They are a quality football club with a fantastic stadium, pitch and support.

“Their quality and movement was too much for us today and we only had a half a team out, with no disrespect.

“We didn't come here thinking we were going to win – you just try your best.

“No one's heads are down. It was still a joy to play here today no matter what the score was.

“Deji's (Oshilaja) early miss was probably the worst miss of the season – an awful miss. He has to hit the target and silence the crowd.

“He doesn't mean to miss but he has to score.”

The Stags side showed seven changes ahead of a week in which they play three times in seven days.

“It was always the plan whatever the situation was as it was a big ask to come here today then play again on Wednesday and Saturday,” he said.

Mansfield went to St Andrews with the pressure of the relegation battle finally lifted and Garner said: “I watched the Bristol Rovers v Reading game yesterday and I am delighted we are staying up. “It is a massive achievement for us and the relief is unbelievable.

“Going back down to League Two would have been an absolute disaster.

“It has been difficult. This has been the hardest time of my career and the gaffer's career as well.

“We have all suffered. There has been a lot of moaning and falling out with staff, we don't want that any more.

“What happens in the office stays in the office but it's been hard trying to find a way to get a team and how to play and get a result.

“We've been together a long time and we are friends. We will always stick together, but this has been tough.

“But we still found a way, no matter what way it is, to stay in League One next season and that is absolutely magnificent – I can't wait.

“It has been a mixed season – absolutely fantastic up to December/January. We were up to sixth in the league and absolutely flying.

“Then, wow, it was an absolute disaster – a nightmare with the games we have lost and the struggle that we've had.

“It has been the longest three months of my life.”

He added:“Looking back, losing Lee Gregory was massive. He was playing so well at the time.

“You can make excuses but he was a massive player for us and up to then he was absolutely fantastic. He and Will Evans had a really good partnership and he was scoring goals.

“We had got 37 points for a reason. We were playing well and doing well.”

Stags were backed by yet another huge away following on Sunday and Garner said: “A massive thank you to our fans. They have been absolutely magnificent to us.

“You will always get the odd one or two who moan, but they are entitled to this year.

“They would be entitled to give us a bit of a slaughtering if they wanted to. But I don't think they have. They knew we were struggling and they knew we were trying.”

On Sunday Oshilaja headed a great chance just wide on 10 minutes after Stags had withstood some early pressure.

It was a miss Mansfield would go on to regret as Anderson opened the scoring midway through the first half when Willumsson flicked the ball into his path.

Jay Stansfield fired wide minutes later after Tomoki Iwata won an initial header.

But the hosts doubled their lead when Willumsson poked a loose ball home after Christy Pym had saved an Ethan Laird header.

Pym kept out a Dowell strike as City started the second-half strongly.

And the rampant hosts got their reward when Dowell beat Pym after a good ball by Paik Seung-Ho on 50 minutes.

It was four seven minutes later when Iwata kept his cool to beat Pym and complete a day to forget for Stags.