MADRID, Feb 23 (Reuters) - Atletico Madrid's La Liga title challenge faltered when they slumped to a shock 3-0 defeat at Osasuna on Sunday that left Real Madrid three points clear at the top.
Champions Barcelona and Real were held to draws at Osasuna's El Sadar stadium in Pamplona earlier in the season and Atletico fell behind in the sixth minute when Alvaro Cejudo arrived unmarked at the back post at a corner to volley into the net.
An error by fullback Juanfran allowed Emiliano Armenteros space to score with a long-range drive in the 21st minute and Roberto Torres nodded a third goal three minutes before the break.
It was the first time Atletico conceded three goals in the first half since Argentine coach Diego Simeone took over at the end of 2011.
Simeone rested several regulars before bringing on playmakers Koke and Arda Turan and attacking midfielder Raul Garcia in the second half.
Atletico forward Diego Costa, who has 21 goals in La Liga this season, toiled up front but a typically gritty defensive performance from Osasuna kept him at bay as they climbed to 12th on 29 points.
Barcelona, Real and Atletico were level on 60 points before the latest round of matches but after Real cruised to a 3-0 win over Elche on Saturday, Barca were beaten 3-1 at Real Sociedad as coach Gerardo Martino's decision to rest key players backfired.
Barca and Atletico won impressively in midweek Champions League action but were unable to carry their form into the weekend.
Real, who are unbeaten in 26 matches in all competitions and visit Atletico next Sunday, are top on 63 points with 13 games left. (Reporting by Iain Rogers; editing by Tony Jimenez)