While I agree with most of the posts, that is a pretty big risk to take. Jones and Evans are injury prone in general. It is not just because of going all out in matches, but in general, both are very injury-prone. Add Chris Smalling to the list - I don't know what happened with him, but he became pretty bad (almost woeful) along the line. Bad reading of the game, and bad positioning. Injuries haven't helped him too.
Jones, despite his injuries, has been excellent, and has potential to be world-class. I would prefer Jones anyday over someone like, say, Mangala. The only young defender who is on the same level is Varane, but it doesn't seem that way with Jones due to the constant injuries he picks. Evans, when fit, is also brilliant in a 4-man defence.
However, assuming we get into Champions League next season, we can't really go with this defence. I'm not talking about quality here, but quantity. You can't have matches from BPL, Champions League, FA Cup, Capital One Cup and the like, and have 6 defenders where 3 senior defenders are constantly injured. We'll never get a constant defensive pair, which is bad news when Central Defence is concerned.
Most good teams in general, have had constancy in defence. We haven't really achieved that due to injuries. And considering our current defence, it is doubtful we will. Hence the need to get a new central defender. Options vary from Hummels to Shawcross to Vlaar. Vlaar is out, mainly due to his transfer value and age. Between Shawcross and Hummels, I'd probably go for Hummels. Remains fit most of the times, commanding at the back, solid, and doesn't make too many mistakes. With him next to Jones, while Evans is used for rotation, defence can be pretty solid for some time to come, while at the same time giving our youngsters gametime in cup games. Rojo will probably used at both LB/LCB depending on necessity.
