Defender Jeison Murillo saw red as Inter Milan passed up the chance to clinch a top-four Serie A finish at Lazio.
Miroslav Klose's fifth goal in as many league games and Antonio Candreva's late penalty saw the home side clinch a 2-0 victory at the Stadio Olimpico on a night when Murillo received his marching orders for two bookable offences.
Lazio, who saw coach Simone Inzaghi sent to the stands by referee Luca Banti, went ahead with just eight minutes on the clock when Germany international Klose ran on to Senad Lulic's through-ball and shot right-footed past keeper Samir Handanovic.
They continued to enjoy the better of the game and Handanovic had to claw Candreva's long-range effort out of his top corner with 28 minutes gone.
Candreva turned provider seconds later, crossing for Milan Bisevac to head wide, and striker Keita tested Handanovic from distance 14 minutes before the break with Lulic once again the creator.
Inter's Stevan Jovetic forced Lazio keeper Federico Marchetti into a 51st-minute save with a left-foot drive from the edge of the box, and Ivan Perisic called upon Marchetti once again 14 minutes from time with the visitors pushing hard for an equaliser.
But their hopes died when Murillo, who had been cautioned two minutes earlier for a foul on substitute Stefano Mauri, conceded a penalty for a challenge on Keita and was dismissed.
Candreva duly obliged from the spot to wrap up the win which eased Lazio into eighth place, three points behind AC Milan with two games remaining.