Ryan Bertrand believes Chelsea made a mistake in letting him go, but it is a desire to improve rather than prove anyone wrong that is driving on the Southampton and England left-back.

Eyebrows were raised last year when the much-vaunted 25-year-old departed Jose Mourinho's men for St Mary's, where a summer talent drain left onlookers predicting a season of strife.

However, Southampton have proved the "perfect match" and provided Bertrand with everything he hoped for - stability on and off the field, plus the stage to play regularly for an ever-improving side.

The initial loan move was made permanent in February when Saints forked out £10million, ending his long association with Premier League champions Chelsea.

"For me it wasn't a case of 'my career didn't go right, I'm not playing for Chelsea'," Bertrand said.

"I know personally I should still be there and I should still be playing but it is no drama. That is football and these things happen.

"I am fantastically happy at Southampton, playing week in, week out and developing as a footballer and really enjoying life.

"I know in myself - that's my inner confidence, I have the capabilities.

"It's nothing to do with my capabilities that I'm not there, it's purely circumstance."

Bertrand has certainly proved his worth since moving to Saints, earning an England recall and a place in the PFA Team of the Year - the only non-Chelsea player to feature in the back four.

"That's not really in my mind to go out and prove people wrong," he said.

"I've no grudges, no chip on my shoulder about showing him 'look, I'm better than him' - it was just about me. That was the whole decision.

"As a footballer you can't get too carried away or too attached.

"I would play there and was happy, but now I play at Southampton I really feel part of it. I really feel like a footballer.

"When the team gets a win and you are playing consistently, you feel good about it. You get a day off the next day and you feel like you deserved a day off."

poll loading

Will Didier Drogba return to Chelsea as a coach?

Certainly no one would have begrudged Bertrand a day or two off after the Champions League final of 2012.

Roberto Di Matteo's bold move to give the left-back his European debut at the final hurdle paid off, impressing in a more advanced role as Bayern Munich were edged out at the Allianz Arena.

"The whole achievement of the Champions League year (is something) I become more and more in awe of it the further it gets," Bertrand said.

"At the time it went by so quickly and you are aware it's the biggest club competition, but the further you get away from it, the more respect you have for it in a way, when you start to realise the greats and the teams that have won it."

Moment of glory: Roberto di Matteo lifts the Champions League trophy

Surprisingly, Bertrand has never watched the Champions League final back - something he suggests may subconsciously be down to a determination to strive for more.

That hard work paid dividends this season, with his Southampton form resulting in a first international appearance in two and a half years.

Now, a first start is on the cards in the Euro 2016 qualifier in Slovenia or Sunday's friendly against Ireland.

The left-back revealed he had been eligible for this weekend's opponents through his late grandfather, who hailed from Crumlin, Dublin, and knows the Aviva Stadium encounter will provide an interesting test.

"It will be a very competitive game," Bertrand said. "They are two sides that want to go out to win and it will be more than just a friendly.

"We want to keep our good form going. In the qualifying campaign we have a 100 per cent record and we want to keep that (form) going."