* Champions on brink of title (Adds quotes, details)
By Daniel Alvarenga
LISBON, May 11 (Reuters) - A stoppage-time goal from substitute Kelvin handed Porto a dramatic 2-1 home win over fierce rivals Benfica on Saturday that put them on the verge of clinching a third consecutive Portuguese league title.
The two teams were undefeated going into the penultimate game of the season and victory gave leaders Porto a one-point advantage over second-placed Benfica.
The majority of the Dragao stadium's 50,000-capacity crowd were ecstatic at the final whistle while visiting coach Jorge Jesus sank to his knees in disbelief when 19-year-old midfielder Kelvin struck with a fierce, diagonal left-foot shot.
"This was an historic goal for me at the start of my career," Kelvin told Portuguese television. "But we have to keep focusing because we still have another match to go to seal the championship."
Porto had most of the possession in a cagey affair but Benfica, who meet Chelsea in the Europa League final in Amsterdam on Wednesday, scored from their first chance in the 20th minute.
A long throw-in caused havoc in the home defence and Lima fired in from close range after pouncing on an Ezequiel Garay shot that skewed off a defender.
Porto hit back five minutes later when Silvestre Varela's low cross deflected off Benfica right back Maxi Pereira and into the net.
Coach Vitor Pereira, who shed tears of joy after Kelvin's winner, said his Porto side never stopped fighting.
"We looked for the victory until the last minute and got rewarded," he added. "It's been such a tough championship and it will keep being so because we still have a final game to play."
The champions travel to third-placed Pacos de Ferreira in their last fixture while Benfica host second from bottom Moreirense.
The fans were on the edge of their seats throughout a tense 'Classico' that summed up a close-fought season.
"We had to risk bringing someone like Kelvin in, someone with his irreverence who comes into a game like this and does something outrageous like that," Pereira said. (Editing by Tony Jimenez)