-- my thinking is what QuincyAbeyie said. If replacing Trossard results in Martinelli being benched, we've done very well. Even if it mounts more of a challenge to Martinelli and he kicks on into higher gear, we've done well. Trading Gabby for someone who might be slightly better than him once they've bedded in is not going to move the needle.
Replacing Martinelli with a bona fide superstar player, like Kvara, Vini, Mbappe, or if a gamble on someone basically at his level now really paid off big time, then sure. But that's not really indicative of a major weakness in the squad, and its not something you can really plan for or predict. Just gotta make the best signings you can and hope for the best.