Question about Oracion seis...?

I just come to the nirvana part of Fairy Tail and I got a question about Oracion seis. I can't understand why Brain said no one is faster than Laser and asked him to get the coffin if Laser is not really fast and just use his magic to make his opponent slow, ? as the leader of Oracion seis, Brain didn't know Laser's real magic? and if Laser is not really fast, how can he save the time to get coffin?