Vela has looked useless every time I've seen him, DM...
Yes, player in form when joining the club, he looked VERY good, player getting 10 minutes in one game, 2 months since his last game...... doesn't look good. Not even slightly surprising. He frequently just doesn't give people a chance. Fergie's no girl about it, he gave Obertan a chance and a few games, didn't show much, didn't get much after that. Anyone he actually buys, or anyone he thinks has a shot gets a chance and a few games.... Wenger buys guys in then gives them 30 mins after playing basically no games for a year and then goes.... you suck and sends them away.
Problem is with say Vela he was on the bench a lot so wasn't even getting reserve games. Same with Eduardo, he actually looked much sharper in preseason and cup before he finally became almost first time just before he broke his leg, when he was still excellent. After his injury he never got anything close to a run of games.
Vela IS an excellent player, but Wenger did the usual, buy a striker, give him barely any game time, force him into a new position, expect utter brilliance.... ignore till he beg's to leave. Other little issue is say West Brom bringing him in expected a left winger and he played deep rather than as a front man. In a 4-4-2 with a good support striker he looks brilliant, on the wing, or lone striker he won't look great.
Then you've got the really simple thing, Walcott given unwaivering support is utterly awful, and Vela looks better than him with no form, no match fitness and out of position.... how would Vela compare with 10 games under his belt, support from the manager and match fitness. He's better than Walcott at his worst... at his best, we've only seen it a few times and he makes Walcott look like an absolute turd. I'd MUCH prefer to give Vela 10 games, see if he does come good, THEN get rid of him than persist with Walcott who we know is utterly useless. One is TRYING to improve, one is going no where.