Chelsea has agreed to pay the 15 million euro release clause in the coach's contract with Porto, according to reports by the national news agency Lusa and several newspaper websites. Villas-Boas has a contract at Porto through 2013.

Porto officials could not immediately be reached for comment. The club would have to announce the completion of any deal to the Lisbon stock exchange, where it is listed, but had not done so by midday (1100 GMT).

The 33-year-old Villas-Boas, a former assistant of Jose Mourinho at Chelsea, has been singled out as one of Europe's most promising young coaches after guiding Porto to the Portuguese league and Cup and the Europa League title last season -- his first in charge at the Portuguese club. He was the youngest coach to win a UEFA club competition.

If he moved to the Premier League, it would be a huge career leap for someone with just two seasons under his belt as a first-team club coach after moving to Porto from Portugal's Academica.

Chelsea is looking to replace Carlo Ancelotti, who was fired last month after his second season at Stamford Bridge ended without a trophy.

Dutch coach Guus Hiddink was also linked with a return to the Blues, where he won the FA Cup as a caretaker manager in 2009.

Villas-Boas was a scout for Mourinho at Chelsea and, later, at Inter Milan. Mourinho, who is now at Real Madrid, moved in 2004 from Porto to Chelsea where he won back-to-back Premier League titles.

Villas-Boas, who speaks fluent English, had also worked with Bobby Robson during the English coach's spell at Porto's Stadium of the Dragon. He coached the British Virgin Isles at just 21.

Porto ended the past season unbeaten in the domestic championship with 27 wins in 30 matches. In Europe, it recorded 14 wins in 17 games, scoring 44 goals with an attacking style of play favored by Villas-Boas.

Porto became only the second Portuguese club to finish a league season unbeaten, after Benfica's 1972-73 team.

"I don't approach football with only a tactical approach -- you can achieve success through various means. What I like is to make my players give their most but I give them lots of room to maneuver," Villas-Boas said on the eve of the Europa League final. "I try to promote their talent and feel free to make the right decisions. I'm no dictator."