Marquez took advantage of poor marking to glance home a header from Xavi Hernandez's inswinging corner in the 63rd minute, while Eto'o scored against his former club with a long shot in injury time on Saturday.
Referee Rafael Ramirez Dominguez reported after the game at Mallorca's Ono stadium that some home fans racially taunted Barcelona's Ivory Coast midfielder Yaya Toure when he was replaced by Edmilson in the 69th minute.
Toure will not play for Barcelona for a month as he joins his international teammates today to compete in the African Cup of Nations.
Meanwhile, third-place Espanyol extended its unbeaten league run to 14 games with a 3-0 win over fourth-place Villarreal. Raul Tamudo scored twice to rise to the top of the league's scoring chart with 10 goals this season, level with Sevilla's Luis Fabiano. Valdo Lopes netted Espanyol's other goal.
Madrid, which hosts Zaragoza on Sunday, has 41 points. Second-place Barcelona's third win in nine matches on the road this season lifted it to 37. Espanyol has 36, four more than Villarreal.
Barcelona lacked injured forwards Lionel Messi and Ronaldinho, who has missed seven of his team's 18 league matches this season. Striker Thierry Henry, who hadn't played since November 24 due to back pain, reappeared as a 64th-minute substitute.
