Walcott is utterly utterly utterly useless as a central striker regardless of what he thinks his role is. He's lazy, weak, stupid, can't hold up the ball, has no strength, doesn't make good short runs into space. He runs in behind... that is his game and career summed up.
Against Chelsea Walcott was truly abysmal playing centrally and he looks that way in every game he starts centrally. He physically can't play that role at all.
As for Ox he's played exactly the same way since he joined, all pace and energy. Except for the one cross that almost got deflected in everything was done with huge enthusiasm and no quality. Every performance is effectively the same, he'll get into some dangerous positions, take some wild shots but is ultimately ineffective. He has 3-4 games a year where his overall input is positive for the team, many more it's negative.
He started against West Ham, was woeful offensively and his sloppy conceding of possession led directly to the second goal where after giving it away for no reason at all he gave up on it instantly, made zero effort to get back. That sums up last season for him even in the games he scored he gave away the ball with a stupid attempt to run past a player or a woeful touch in a dangerous possession that led to a goal against us.
If he learned to control himself just a bit, not run headfirst into trouble over and over again and significantly improve his shooting then he has a physicality, pace, strength and stamina, that very few have. The biggest issue I have with him is he really hasn't improved his game, changed his game in the slightest since the day he joined. He's the same 3-4 good games a season 10 average games and 10 bad games a season player he's always been.