Of course they could - and would have been.
As others have pointed out we dominated that game. You claim the problem was shielding our defence:
- how would playing a 5' 4" Junior have helped with protecting our defence from the ariel bombardment up to Cisse, Ba and Ameobi?
- are you really suggesting that when we are under pressure in a vital match against one of our big rivals we should turn to an 18 year old (yes EIGHTEEN year old) CAM as the solution to our defensive problems?
Of course there is room for improvement - there is always room for improvement - but that doesn't mean that Junior and Barkley are the solution at this time.
The role of a central midfielder in the formation we're playing, where the full backs bomb on and the two wingers drift inside to create an attacking four is to a) cover the gaps left behind when we push up, b ) slow down their attacks by getting in the way and c) recycle posession and only d) push up to join the attack. Osman and Neville aren't mobile enough to do the running for 90 minutes that requires. Newcastle and Swansea both walked through them like they weren't there at times.
And, more importantly, they both lost posession cheaply, which is the one thing you can't do in that position. The number of times Howard tried to play from the back and then we gave it away when it came to those two was too many. Newcastle's first goal was when osman was caught on the ball and swansea's best spell was when neville kept passing the ball to no-one.
Players in there who can run around for 90 minutes and always find a team mate when under pressure (like Gibson for example) would make a huge difference. That's why I think Junior would help protect our defence. Newcastle can't bombard us if they don't have the ball.
Also the problem is we don't have two Fellaini's. Ideally we'd be able to play him both in the Osman role, cleaning up and passing forward in front of a deep lying midfielder and in the AM role but obviously we can't. So we have to sacrifice him in one of those roles. And the question is will the drop off quality from him to osman in CM or him to Naimsith/Barkely in AM be more drastic and so cost us the most? I'm on the fence on that one. But it's another reason why I think Barkley and Junior should be looking at that gibsonless midfield and going 'I can get a game here'.