Sadler is seen as a player with promise at St Andrews

The 22-year-old, who had a year left on his old deal, has committed himself to the St Andrews club until 2010.

Sadler started 36 games for Birmingham last season as he helped them to promotion back into the Premier League at the first attempt.

"I am confident that, given a chance, I can play well in the Premier League and I am looking forward to the challenge," he told the Blues website.

"There is a lot to prove for some of the lads and it's a good stage on which to do that."

There is only one actual objective and that is to stay in the Premier League Mat Sadler

Sadler has come through the Blues ranks and insists survival will be the priority on the club's return to the top-flight.

"It was just important that we were back in the top division and I am happy that I played a part last season," said Sadler.

"But I am more looking forward to next season.

"There is only one actual objective and that is to stay in the Premier League.

"You can't really look any further that that because it would be unrealistic to do so.

"That may not sound as ambitious as some would like to hear but first and foremost survival is what we have to achieve."