Beltran, who is bothered by a sore left hand and an aching left knee, went 0-for-5 in Friday's 5-4, 13-inning loss to the Milwaukee Brewers. He is hitless in his last 13 at-bats and hasn't had an extra-base hit in 48 trips to the plate.
Matheny is hoping the rest will help Beltran both mentally and physically. Beltran's average sits at .261, its lowest since May 1.
Beltran, who had a cortisone shot to help his hand, got off to a strong start this season. He was batting .312 as late as June 29.
"There have been some physical things that have been bothering him and sometimes those lead to mechanical adjustments, more than are necessary," Matheny said.
Beltran is 11 for his last 80 at the plate.
Matheny indicated that he might give Beltran more than one day off, if it will help down the road.
"We're going to start with today and just see how things go down in the cage," Matheny said. "I know he's going to fight a prolonged rest, claiming that's not what he needs. We'll see how his work goes."
Beltran sat out Monday's and Tuesday's games but returned Wednesday with an 0-for-4 performance against New York.
"He's on the brink of being able to head in the right direction," Matheny said. "We're going to watch him physically and give him time to get it worked out mentally. He's had some very good at-bats for us -- and I see that happening again soon."