كتب : Mohamed Sabe
The title holders handed over the Primera Liga summit to Sevilla after a 2-1 defeat on Sunday.
"We had the chance to kill the game, but we were unable to take it," Rijkaard told a press conference after the game.
Barcelona had taken the lead through Ronaldinho in the 13th minute but the Brazilian magician squandered an opportunity to double the lead when he wasted a penalty kick in the 27th minute.
The European champions also couldn’t make use of the one-man advantage after Sevilla defender Ocio was sent off for the challenge on Ronnie.
"We started well, but after the [missed] penalty, I thought they improved and we did not.
"It is a fact that we have thrown away a wonderful chance. We did not kill the game, and then we should have upped our game like they did," the Dutch boss added.
Unlike Barcelona, Sevilla made the best of the situation when the Catalans were reduced to nine-men after Ludovic Giuly and Gianluca Zambrotta were sent off in the second half.
"Sevilla deserve to win because they fought, they are a team that play very well," he said. "They are very well-organized and disciplined, and everything is working."
Barcelona now trail leaders Sevilla by one point.