"The longer he goes," manager Bob Melvin said, "the rustier he can get."
Melvin said he is "mildly concerned" about Wells' lengthy absence from games but he plans on getting him a start against a left-hander as soon as Wednesday.
"Obviously you'd like someone to be current," he said, "but there's not much we can do about that. He's here for a reason and he hopefully has a good batting practice."
Wells, traded to Oakland by the Blue Jays for cash on Monday, was designated for assignment by Toronto before ever getting into a game. This after he had already been designated by the Mariners on the last day of Spring Training.
The 28-year-old spent the last week in Seattle, getting in work at a local high school while "champing at the bit to get out on a baseball field and play baseball," he said.
"You have to keep a solid mindset, not let any outside distractions in or get off track from what you want to accomplish," Wells continued. "I'm glad Oakland took a chance on me here.
"I wish there was some way, during that waiver period, where you can still get at-bats in an extended setting, because it really puts guys like me in a situation where you haven't seen live pitching. I don't know how far behind I am, but I'll wait my turn as far as getting comfortable in a spot."
It's not certain Wells will even have a chance to get comfortable in his new home, with outfielder Yoenis Cespedes (left hand) expected off the disabled list Sunday.
Wells pinch-hit for Coco Crisp in the sixth inning of Tuesday's 13-0 win and flied out.
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.