Jarvis has made just one start for the Hammers since moving from Wolverhampton Wanderers for £10m in August.
McDonald thinks that Jarvis will need to work hard to nail down a regular starting birth in Sam Allardyce's side.
The Hammers' number two told reporters: "Matt's biding his time. There's a lot of competition but he's definitely ready to go back in.
"Our gaffer has always had a reputation that if you play well you stay in the team.
"Whoever can't get in, and it might be a record signing, they have to wait for their chance to come.
"And when it does come they've got to be ready."
The 26-year-old is in the Hammers squad for the London derby against Queens Park Rangers on Monday night.