Duffy was scratched from the lineup for Saturday's Grapefruit League game against the Detroit Tigers. He was to undergo more testing Saturday on the hamstring injury that has sidelined him for most of the spring.
"I would imagine we would take our time with this and try to get it under wraps," Cash told reporters, according to the Tampa Bay Times. "We didn't want to rush it, but our best team is with him on the roster."
Duffy has appeared in just two games this spring, including Thursday, when he made his return from the injury. He got an additional nine at-bats in minor league games on Friday. The team wanted to see how he felt Saturday after two straight days of action.
"I think we did everything," Cash said, according to the Times. "The training staff did a great job, Matt did a great job of trying to get back. Time just beat us up a little bit."
Duffy hit .294 with 22 doubles, four home runs and 44 RBIs last season for the Rays. He led the team with 148 hits.