Quite often it is not the team that you expect you could potentially 'slip up' on that causes the upset. You're certainly right about the Barker vs Knox fixtures - especially now with the 2 round calendar. I think that out of the 4 years it's been implemented we have had an even split of victories between both schools (not including this year). In 2011 Knox beat Barker in round 1 37-12 I think (something along those lines). Barker went on to produce a rather mediocre season and then finished with a surprise win over Knox. The following year the exact opposite happened. Truly anything can happen in those games - and that is something that Cranbrook can take some comfort in as the gap between Barker and Knox (in terms of confidence and ability) seems to be thinning throughout this season.
Will this weekend be a good game? Perhaps, but you'd be banking on cranbrook to win. Kirkby and Smerdon are back for barker this time and the forward pack for barker has matured and settled a bit since their last encounter with cranbrook but I don't think it will be quite enough. If anything will win it for Barker it will be the fact that they will play with as much zeal as they did against trinity a man down - knowing that their season is on the line.
If I were their coach I would be constantly reminding the boys of that in training now. Focus on your game, work to your game, and play extremely physical. You come out hard in the first 15 and rattle the Cranbrook boys, put some points on early and all of a sudden they're reminded that they've got something to lose and you don't. Easier said than done but if the Barker forwards can knuckle down like they did in those last 15-20 minutes against Trinity then they certainly could win, but they'd need to maintain it for a whole game. Jono Green needs to step up again and be vocal, because it's something these boys have been lacking this year.