Does a player have to play in ERCC (HCup) to improve internation chances?

With the news about possible the Welsh players returning and some people suggesting that they should go to Ospreys and Scarlets to play top European rugby it got me thinking about sometime I've wondered about for a while, Does a player have to play in ERCC (HCup) to improve internation chances?

Same happens in Ireland with it suggested that Henshaw and Marmion should move to a province in the ERCC to improve thier Ireland chances.

But does it really matter if a player plays in the ERCC to increase chances of National selection and does it really improve a player that much?

Personally I think its a bit over hyped, Taulupe Faletau has never played in Hcup (as far as I know) and this hasn't held him back for Wales and he even started for the Lions.
In reality for a lot of clubs its only 6 extra games a year and while they may be against higher quality teams, some times the teams are not intrested in the Cup if they lost the first few rounds and cannot qualify, or the player may even be injuried and miss the games if they moved.

Wales will only have two teams in ERCC this year, and possibly same next year, same with Italy and Scotland only having one. Ireland are not always going to get 3 teams in, so is this going to impair player development?

So is playing in ERCC important for player development or is it just a stepping stone that helps but can be overlooked?

Faletau has played Hcup rugby, but I agree, particularly as the challenge cup is getting stronger.

In England's case the following were selected for the last 6N or summer tour without their clubs having played Heineken Cup rugby that season:

Joe Launchbury
James Haskell
Marland Yarde
David Wilson
Dave Attwood
Rob Webber
Kyle Eastmond
George Ford
Anthony Watson
Matt Mullan
Henry Thomas
Chris Pennell
Kieran Brookes
Nathan Catt


Additional players brought in for the game against the Barbarians were:

Jonathan Joseph
Semesa Rokoduguni
Ollie Devoto
Elliot daly
Joe Simpson
James Gaskell
Rob Miller
Ross Harrison
Tommy Taylor
Michael Paterson