Newly-promoted Premier League side Middlesbrough are interested in signing Chelsea defender Tomas Kalas, the 23-year-old's agent has confirmed.

The centre-back joined Chelsea from Sigma Olomouc in 2010, but has endured a tough time breaking into the Blues' first-team - spending much of his career out on loan.

The most recent of those loan moves was at Middlesbrough where Kalas played a key role in helping the club gain promotion to the Premier League last season after making 26 Championship appearances.

Despite only signing a new contract at Chelsea last year, which will keep him at the club until 2018, the 23-year-old's agent Mithat Halis has revealed that Middlesbrough are interested in recruiting the versatile defender on a permanent basis although his client remains content at the Bridge.

"Kalas wants to stay in England next season, preferably in the Premier League," he said.

"He is happy at Chelsea but Middlesbrough are interested."

After joining Chelsea six years ago, Kalas was sent out on loan to Dutch club Vitesse Arnhem for two years before returning to Stamford Bridge for the 2013/14 campaign.

Former Blues boss Jose Mourinho handed the defender his debut in Chelsea's 2-0 Capital One Cup win against Arsenal before he made his first Premier League start in another 2-0 victory, this time against Liverpool in April 2014.

Those appearances didn't stop Kalas from being sent on loan again, however, as a move to FC Cologne and then Middlesbrough followed.

Speaking at the end of last season, he told the Evening Gazette: "I don’t know how many games I’ve played since I came, probably around 40, which is not bad in one and a half years.

"That’s why I came here, to play games, and hopefully I’ll keep playing next season - maybe here.

"If I could get the deal (to move to Boro permanently) I would really think about it. Yes, why not!"