It doesn't seem at all controversial, or even the smallest of issues, that Martinez would be planning to set out his "strongest possible side" for the derby, despite the short turnaround for the FA Cup. Of course he will want a strong side against Liverpool. But the key word is "possible," since injuries will limit a few of his choices on Wednesday night. Martinez did plan to put his strongest possible sides out for this week's two big matches. Injuries threaten to complicate his plans, but not destroy them.
He wisely rested Barry and Lukakau against Southampton, and played Barkley only as a sub. McCarthy was suspended, so he rested, too. Baines, Jagielka, Lennon, and Cleverley were rested because of injuries. So really, it's these last four who are questionable for Wednesday night. His earlier comments implied that Jagielka and Cleverley probably won't have recovered sufficiently by Wednesday. Saturday? Maybe. Coleman isn't possible. Gibson and Oviedo were not, presumably, significantly injured, so they're available.
That leaves Baines and Lennon as the key question-marks for the "strongest possible side" for the derby. Will it be Baines or Oviedo? Will Lennon start instead of either Mirallas or Deulofeu? Also, will Pienaar get on the field for 15-20 minutes Wednesday, with a view to starting on the left with Baines at Wembley?