"There's not much between their scrummaging," said Connolly of the difference between Blake and Shepherdson.
"We probably think that he (Blake) gives us a little bit more around the field sometimes.
"But they're both 23 and they've both got a fair future - all of them.
"Holmesy has to improve his scrummaging. Michael (Foley) and I have spent hours talking about that with the three of them. It's their first real year of Super 14 and I think they've made great advances but the best is yet to come."
While conceding that Blake was not at his best against England in June, Connolly said the 130kg prop had earned his right to return to the national team.
"He's playing close to the best loosehead in the world (Tony Woodcock) this weekend and I think that's a great opportunity to measure himself against that sort of player," he said.
Chris Latham; Mark Gerrard, Stirling Mortlock, Matt Giteau, Lote Tuqiri; Stephen Larkham, George Gregan (capt); Greg Holmes, Jeremy Paul, Rodney Blake, Nathan Sharpe, Dan Vickerman, Rocky Elsom, George Smith, Scott Fava.