Anderson Talisca came back to haunt parent club Benfica, netting a stunning stoppage-time free-kick to earn new side Besiktas a 1-1 Champions League draw.
The Brazilian joined Besiktas on loan from the Portuguese giants last month, and the Eagles may be regretting that decision after he denied them two points in Tuesday's Group B opener.
It looked as though Benfica, quarter-finalists last season, would get their 2016-17 campaign off to a winning start after they held the lead given to them by Franco Cervi's 12th-minute goal.
But in the third minute of stoppage time, Talisca stepped up and sent a superb, swerving 30-yard free-kick into the bottom-left corner to earn his new employers a share of the spoils.
The home side were without a trio of injured forwards in Jonas, Kostas Mitroglou and Raul Jimenez while head coach Rui Vitoria was serving a touchline ban having been sent off against Bayern Munich in the quarter-final second-leg defeat in April.
The hosts coped manfully without those enforced absentees, but ultimately it was a man they chose to let go that cost them a potentially crucial two points in a group also containing Dynamo Kiev and Napoli, who won 2-1 in Ukraine.
The visitors looked the more assured side in the opening exchanges, but it was Benfica who broke the deadlock as they took advantage of a couple of defensive errors.
Hesitation from Marcelo under a long ball allowed Eduardo Salvio in behind, and his fierce shot from a narrow angle was parried back into danger by Tolga Zengin, with Cervi on hand to lash home.
Ricardo Quaresma - roundly whistled by the home fans due to his time spent at Sporting CP and Porto - stung the palms of Benfica goalkeeper Ederson with a 30-yard free-kick on the half-hour mark as Besiktas looked to find an equaliser before the interval.
In the 39th minute Goncalo Guedes drew a save from Zengin, who this time managed to hold on with Cervi looking to pounce again. The keeper flew to his left to push behind a rasping effort from Andre Horta in the last action of the half.
Besiktas coach Senol Gunes replaced Oguzhan Ozyakup with Talisca at the break and the Brazilian felt he should have had a penalty after going down under a clumsy challenge from Victor Lindelof.
In a second half of little goalmouth action, the visitors ought to have equalised when Tosun, scorer of four goals in three league games this season, hacked wildly over from close range following Vincent Aboubakar's lay-off.
Benfica should have made the game safe late on when Guedes robbed Quaresma only to be denied by a sprawling Zengin one-on-one, and they were made to pay for that miss when Talisca intervened deep into injury time.