The Croatian striker, who joined the Hammers on a free this summer after leaving Fulham, is training hard to catch up to the rest of the squad but this weekend's Premier League fixture against Everton may be too early for him according to manager Sam Allardyce.
"Mladen Petric is training every day and trying to overcome the every day fatigue. He is going through a pre-season and that leaves you tired," he said.
"We're then waiting to find his recovery is quicker and he's into the football as well as the physical side. He's enjoying being back with a group of players he can mingle with rather than being stuck in a park or gym.
"We're hoping he can make an appearance in or around for the Cardiff game [on Tuesday night]."