No, Wenger didn't NEED to play Bendtner upfront in this game, he CHOSE to. He CHOSE to play GIroud against a woeful Norwich side and an even more woeful Palace side when he could have rested Giroud for the "easy" games and played him against Chelsea. Wenger is basically the only manager alive today who would choose the Chelsea game to rest his top players and not the two ridiculously easy games out of the previous three games knowing full well this game was coming up. But as it goes, Wenger is a moron. Since 04, we've only not had a side capable of winning a league title for 3, maybe 4 of those seasons, still a side that could do better than 4th and still a side that could win other cups though.
Wenger's utter mismanagement of the squad during this entire period is the reason we fail to win big games and haven't won a single cup.
Hell look at the carling cup final, we finally got to another final and Wenger played an injury plagued through the season Cesc against a **** Stoke the game before the final. No other manager would have risked Cesc in that game and instead given him the extra days and training and played him in the final. Most managers wouldn't have risked him if that was playing against Utd/Chelsea/Liverpool, let alone an overly physical Stoke side, the final was the far far far more important game.
Only playing for part of a game isn't really being rested either, it's less bad but you still build up to the game the same way, train less usually the day and day before a match, warm up before the game, during the game and then risk injury during the game.
No one expects ANY players to be at their best without any match time, no one expects players to be at their best against the best teams in the league. Ronaldo, Messi, Giroud, Wilshere, it doesn't really matter who, they'll score more or play better against Norwich than CHelsea 99/100 times. So why play an unfit, out of form Bendtner in this game rather than give him a chance against Norwich, and play Giroud against Norwich, and not Chelsea?
AS with Ryo, any player not playing almost at all will not be at their best, it's as simple as that. As per usual Wenger buys someone shows them the bench(if lucky) for a few years, then throws them in against incredibly good opposition with zero form, no match fitness. Yet another player he threw to the wolves last night. As above, Norwich/Palace would be great games to give Ryo a chance to build up some fitness/form, Chelsea is a truly ridiculous game to give him a chance and expect him to perform. Either way it was still Ramsey/Rosicky/Cazorla who were utterly useless yesterday and had most of the ball.