Declan Fitzpatrick is a tighthead who has been spotted doing impressions of a loosehead when injury demands it. They're not particularly convincing ones, although that might have been due to other factors. Fitzpatrick can scrummage, he basically got into this squad on the back of pulverising Embra's front row in the HC SF - and that front row had about a 120 international caps between them. At HC level he's a strong scrummager who makes a few carries and doesn't get made to look like a twat around the park. Whether he can scrummage well enough at the next level, not entirely sure. Whether he can do enough around the park at international level, equally none too sure.
Darren Cave is pretty much an out and out 13. Between injuries and the obvious impediment to out and out 13s in Irish rugby, he's not really had the chance he deserves yet. There are slight doubts about his top-end speed but that's it - he's a very intelligent player who makes a lot of space for players around him, an excellent defender, good feet and can kick if he needs to. I tend to compare him to Conrad Smith - near identical builds, similar playing styles - although he's not as experienced, nor does he possess as good a set of hands, and just not quite as good.