With 20 minutes to go in a game poised at 0-0, a manager should be looking at two options when making a substitution. Either bring on someone to help consolidate our position, or someone who can have an explosive impact on the game. I think it's clear that Jack isn't at a stage in his career to be able to complete either of those tasks. He seems to be someone that needs to start a game, and be given time to understand the style of play and tempo that is required of him. It also gives him time to build his confidence a bit, and not be too worried about making a mistake.
I agree that he didn't look great on Saturday, but I don't think we should be worried at all. I mean what can you expect from a 19 year old lad with next to no top flight experience, being thrown in against the league champions, at a point in the game when they are going to go all out, chase everything down, shut down all of our players and pretty much do anything to score. I know he is a bit of a donkey these days, but I would have brought Bent on, just to keep their midfield looking back over their shoulders more than anything else, and make them worry a bit more about committing numbers forward.
I don't think we can start him just yet, as I think the pace and directness of Gabby and N'Zogbia playing off Benteke is what we need at the moment, but if we get into another run of wins, then why not give him a start. I think Jack is the biggest sufferer of the shambolic early League Cup exit, as those games would have been a perfect opportunity for him to get some real first team experience. Hopefully we will have a decent FA Cup run, and the lad will be able to grab his chance then.