The question now should be, do all mutants have the same behavior? we pretty well know that the scouts were tested time ago, and, we've seen loads of times here in the forum managers complaining when they buy each season a new full 6* team without work as expected xD
Too, can be interesting know if you sold the old STs before buy these new ones.
Then just to clarify, when I say:
"simply they will have a random performance depending of the actual players roles of contribution"
I mean better, "they'll have random contribution role",... not like "they will be always mediocre contributive players", what I wanted to mean, is that a market player, isn't a guarantee, so, exist the option, of course, to hunt a key player achieving 9's and 10's, but, this will depend of the actual team you have, so the variable is wide.
I guess if you change these 2 players for sub's or reserves, its performance and rating will not be the same.