He deserves a chance.
He doesn't need to be the most technically gifted player in the world to play in that position, he just needs to know what his job is and to do it well. Not that he isn't talented, in the games he's played for the first-team I think he's been good on the ball, passed it well and helped to win it back. Its not an easy position to play in, particularly when you've got limited first-team experience and you're being asked to do it at Upton Park against a strong West Ham midfield, but Stewart has slotted in pretty seamlessly and really caught the eye.
None of the current midfield are performing particularly well, what do we have to lose in rewarding Stewart for his good performances in the Cup and giving him an opportunity against Villa?