But fit-again Joel Veltman could be seen getting stuck into what looked a lively, upbeat session at Lancing.
Mitoma has been out for six weeks with an ankle injury and will not travel to Tokyo over the next fortnight for two Japan games.
Head coach Fabian Hurzeler said the winger was 50-50 for Selhurst Park when he spoke to media on Thursday morning.
But there was no sight of him in 18 photos posted on the club website on Saturday afternoon.
By contrast, there WAS a shot of a smiling Brajan Gruda, who has been ruled out of the Palace match but is back on the grass after injury.
Albion have been in close contact with the Japanese FA over Mitoma.
Of course, one theory could be that, if he is ready to play, they have no wish to let the public, or Palace, know about it.
But it appears unlikely he will be involved at Selhurst Park, a venue where – coincidentally – he suffered an injury last season.
That opens the possibility of Hurzeler naming an unchanged XI for the first time.
He could go with the line-up which kicked off the 3-0 win at Leeds and which he did not change until the 81st minute of the contest.
Crystal Palace took off two-goal Ismaila Sarr after an hour of their Conference League win over Alkmaar on Thursday to protect him for the Albion game.
Head coach Oliver Glasner also said Adam Wharton was less than 100% during his brief appearance in that game after a recent illness.