The 28-year-old was denied a move to Manchester City during the recent transfer window, despite having less than a year remaining on his contract and reportedly being desperate to leave the Emirates Stadium.
Nicholas now expects the Chilean to secure his exit in the January transfer window, but believes that manager Arsene Wenger is better off leaving him on the bench in the meantime if he is to continue his recent level of performances.
"Like most people, I think he will be committed to going out to play but, the same as last season, there's an element of disguise about it. He'll stay out on the left, do a little dance with the ball then lay it off rather than really surging into the box and giving his all. If he does that again, then I'd leave him on the bench," he told Sky Sports News.
"People compare his work rate favourably to Mesut Ozil but at least he is going to get the ball and make passes, which is what he's good at. I'm not sticking up for Ozil, but sometimes the movement isn't good enough for him and that comes back to Sanchez.
"When he's not happy he'll just stand on the left, run around a bit to try and win the ball back, but not really give his all to win games for Arsenal. I think we've got three-and-a-half months of Sanchez and then he'll leave in January, when Arsene Wenger will have more time to go and get Thomas Lemar."
Arsenal host Bournemouth on Saturday looking to avoid falling to three consecutive Premier League defeats for the first time since January 2012.