Atletico Madrid conceded three goals in 13 second-half minutes to go down 3-2 against their city rivals at the Bernabeu on Sunday, allowing Real to retake top spot from Barca in the standings on goal difference with just nine matches left.
"I didn't watch it (the derby) because I knew Real Madrid were going to win. I don't know if opponents give 100 percent against Madrid," Keita told a news conference on Monday.
When reporters asked him to clarify his statement he added: "It's only a personal opinion. Madrid players may also think the same about teams who play us because Barca always seem to win."
The Mali international also spoke about Real's 4-2 win on Thursday away to Getafe, who are coached by former Real player Michel.
"The Getafe coach said he would like to see Madrid win the title, and if you say this the day before you play, it's not normal," Keita said.
Barca and Real, who meet at Madrid's Bernabeu on the weekend of April 10/11, have 74 points from 29 matches and are 21 points ahead of third-placed Valencia.
The result could be critical to the outcome of the title race with the head-to-head record between the two sides, rather than goal difference, deciding the winner as happened in 2007 when Real pinched the league from Barca.
Barca hold the advantage at present having won 1-0 at the Nou Camp in November with a goal from Zlatan Ibrahimovic.
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