Agree on the long term outlook, but starting him after last night's performance is quite literally rewarding bad play.Parker, playing at the level he did last season (which was an anomaly for him), over the course of a season, is still likely better than Tarek or any other option we have currently. If that is his floor and we know what his ceiling is, I bet on him returning to prior form (because he is only 27 and would not expect significant decline yet) because that gives us the best chance of fielding the best possible iteration of our team.
He's not a game changing player who gets to play himself into shape in competitive games, so he needs to prove he's back in training and off the bench unless forced into action (presumably like last night, hopefully with a different outcome).
Also not sure Tarek is necessarily worse, haven't seen anything terrible from him in his time here.