I mean, I could understand if we are facing Southampton or sth at home, a team that's decent and could hurt us on the break, which prompts Jose to select Rashford for his workrate. This is Crystal Palace ffs, they've been absolute shambles all season and this is a perfect opportunity following the CSKA game for Martial to continue performing and building his confidence. Even if fitness is an issue, surely a starting berth sends a signal that good performance will be rewarded?
Martial has had a single, solitary league start this season, all other appearances have been sub/cup games. That's squad player status. Pretending that the both of them are equal in rotation is disingenuous. SAF used to do the same, first choice starts in the league, second string play in early cup games and 'easy' CL groupstage matches.