Marquez was following Corsi with less than 5 minutes left in FP2, Marquez is going through the fast left-right and sees the narrowest of gaps and dives into the right hander. He gets level with Corsi near the apex of the corner, Corsi must still be unaware of another rider and when he goes to tip it in he makes contact with Marquez. Corsi is sent tumbling into the gravel at high speeds, not a nice sight!
Even the two Eurosport commentators were questioning his motives. He has now been pushed to the back of the grid as a penalty, thoroughly deserved IMO. I doubt that will make much difference to his race, he will just steam through as usual!