Even if he was with a knock I'd say that if Pep would have fielded Busquets over Keita, our midfield wouldn't have been overrun so badly today. Keita really isn't a real DM. He's more like a box-to-box runner, a player who chases after the opponent and tires them. Busquets, on the other hand, is a destroyer, a very very good one, who positions himself to intercept plays and launch counters. I also think he's a better passer and his height might have been more useful than, for example, Macherano's.