Benfica's Paraguay striker Oscar Cardozo netted twice in the last 10 minutes having pressed defender Marcos Rojo into scoring an own goal after an hour to cancel out Sporting's first-half opener from Ricky van Wolfswinkel.
Cardozo converted a penalty after Sporting's Dutch centre-back Khalid Boulahrouz was sent off after handling a goal-bound shot from Eduardo Salvio and then sealed the points with a neat header in the 86th minute.
The battle for the title already looks like a two-horse race with Benfica and Porto locked on 29 points after 11 matches, the champions having earned a hard-fought 1-0 home win over Moreirense on Saturday.
Sporting, knocked out of the Portuguese Cup and Europa League, the defeat left them in ninth place, are now 18 points behind the leaders.
They have only three wins in 19 matches in all competitions which represents their worst start to a campaign since the league was formed in 1933.
"We were at different levels. We had physical problems and in (terms of) quality to keep the ball and (catch our) breath as we were getting too much pressure from Benfica and paid for our mistakes," said Sporting coach Franky Vercauteren. "It was all a bit too much for us".
Sporting played well in the first half but crumbled in the second. They had deservedly taken the lead through Dutch striker Van Wolfswinkel who applied a classy finish to Diego Capel's cross after half an hour.
But in a Lisbon derby featuring plenty of chances for both sides the second period was commanded by the 'Eagles'.
"We came into the match a bit sleepy in the first half but after the goal we pressed them and kept the ball to ourselves," said Cardozo.
The equaliser came when Liberian-born winger Ola John sent in a dangerous cross from the left that Cardozo mis-headed but defender Rojo deflected in.
Man-of-the-match Cardozo then converted a penalty in the 81st and, with many frustrated Sporting fans having left the Jose Alvalade stadium, struck again five minutes later to give Benfica some consolation following a goalless draw against Barcelona on Wednesday that ended their Champions League campaign.