Pepe LeFrits Could be right but my immediate feeling when Leo came on was that it was just his turn this week.
I think you're right it was Trossard's turn, it had the vibe that with Arteta having dropped Martinelli and re-signed Trossard, he now had to bring Leo on, all else being equal.
Still wouldn't be surprised if we sold Martinelli during the week. I don't think it would be bad business. I really like Gabi and have great disdain for those that heavily criticise him, but clubs rarely go back to players they move on from.