Gagner has NEVER had to face the toughs.
I agree that line will be great to watch when they have the puck. The problem for them will be getting the puck and finding space to play with it before they turn it over.
Gagner has faced top defensive pairings many a time to go with playing the other teams top 2 lines. Horcoff has been hurt many times during Gagner's career, and i seem to remember Penner-Gagner-Brule being the teams #1 line. Gagner even now is not a sheltered player, he plays top 6 opponents. For example Sam Gagner played similar or tougher competition compared to other centers (part time too) Benn, Ribeiro, Vermette, Statsny and Duchene (by alot too), Sharp, P.Kane, Hodgson, Bergeron (although he had a tough zonestart), ect... Sam Gagner by the way had a positive RelCorsi and was a plus player last season to go with easily top 50 production for his position.
I've said it before and i'll say it again the only players the same age or younger to outscore Gagner as centers are Stamkos, Tavares, Hopkins, O'Reilly, Henrique (Parie-Kovalchuck linemates), Stepan (same ppg basically), and Seguin who played RW. Couture and Kane (who played alot of center last season) scored more too but they are both nearly a full year older despite going in the same draft. So basically other than the first 5 centers taken in their drafts we have, Henrique a Calder canidate who had arguably the best linemates in the league, Stepan who's scoring at an identical rate and is a smaller center on a team with a "soft" 1st line center too (they also happen to be a top team), O'Reilly who looks like Bergeron 2.0, and Couture who like i said is older and is a very very good player. Gagner it seems to me is doing just fine if he's in the tier below those guys and is in or even slightly below the next group of up and coming centers with the Henriques and Stepan's of the world. We need to appreciate what we got here and not devalue quality young players like Gagner or Paajarvi just because they can't keep pace with elite players. Gagner in particular has been outstanding up to date for his age. He's not a PKer but he produces at evens and can play quality competition and outshoot them. He's not a Selke caliber two way center but he could easily end up as Stephen Weiss type player.