It's a shame but not the end of the world.
Flyers have Farabee, Cates, Foerster and TK, Tippett, Brink on the right side.
Foerster probably has as much upside, not quite the sniper that Gauthier is, but elite defensive winger as a rookie and scored 20 goals. Gauthier has to prove he's willing to play a two way game, mediocre on defense in college.
Farabee (44), TK (38) and Tippett (36) all scored at 1st line rates (pp/60) 5x5 - median 1st line forward is 48th.
Brink has flashed as a rookie (163), needs to take it to another level next year.
Cates has struggled to score but is elite defensive, possession forward (xGF% 60.47% which is off the charts).
And they already have Michkov and Barkey, in the pipeline.
If Gauthier had showed he was a top six center this would hurt far worse, but Anaheim is already moving him to LW.
This team's real need is a top 6 center to pair with Frost, hopefully a two way player with above average speed.