Pepe rescues point for Real Madrid
Osasuna's Oriol Riera headed in goals in the 16th and 39th minutes before Madrid's woes deepened when Sergio Ramos received his second yellow card in the 44th.
With Cristiano Ronaldo unable to extend his eight-game scoring run for club and country, midfielder Isco Alarcon pulled one back before halftime and passed for Pepe to head home the 80th-minute equalizer seconds after Osasuna's Francisco Silva also earned his second booking.
Co-leaders Barcelona and Atletico Madrid lead Madrid by two points. Barcelona hosted Villarreal late Saturday and Atletico hosts Valencia on Sunday.
''The team demonstrated it has a good attitude, but a draw is like a loss for us,'' Madrid defender Marcelo said. ''We knew that the result wasn't good enough but we reacted too late.''
Madrid's five-game winning run in the league ended at a ground where it traditionally has trouble getting wins. The powerhouse has only one victory in its last six visits to Reyno de Navarra Stadium, where Osasuna turns up the pressure and physical playing style, urged on by its raucous crowd.
Osasuna, which sits just two points above the relegation zone, can boast it has held both Barcelona and Madrid to draws there this season.
Madrid started strong, arriving in waves to Osasuna's area, and Ronaldo had two chances to put his team in front.
But it was Osasuna that struck first when right back Marc Bertran dribbled by his marker before swinging a cross to the far post where Riera was left unmarked to redirect the ball into the net.
Madrid momentarily lost both its verve in attack and composure in defense, and both center backs Pepe and Sergio Ramos got yellow cards.
Riera was left free to double the hosts' lead by nodding in the follow-up of Damia Abella's header from a corner kick that goalkeeper Diego Lopez sprung to palm off his line.
And Ramos soon saw his second yellow card on a questionable decision when Osasuna's Roberto Torres fell after colliding with his arm.
Just when Madrid was at its lowest, Ronaldo dribbled into the Osasuna defense and laid off for Isco to place a right-footed strike just inside the upright and pull one back before the break.
Osasuna still appeared set to get the victory after a placid second half until Silva earned himself two yellow cards in a four-minute span. Isco found the hole left in the defense which Pepe exploited to score Madrid's second.
Also later, Malaga hosted Getafe and Granada visited Rayo Vallecano.