SAN DIEGO -- The Padres dropped two of three at home to the last-place Marlins this weekend, but help is on the way.

Rookie phenom Fernando Tatis Jr. is expected to begin a rehab assignment at Double-A Amarillo on Monday, manager Andy Green said. The 20-year-old shortstop has been out since April 28 with a left hamstring strain.

MLB Pipeline's No. 2 overall prospect, Tatis was a surprise inclusion on the Opening Day roster. He justified that decision almost instantly, posting a .300/.360/.550 slash line in his first 100 at-bats.

Tatis had been excellent defensively and on the basepaths, too, showcasing the five tools that make him the Padres' clear shortstop of the future. In his absence, San Diego asked Manny Machado to move from third base, and he filled the void seamlessly.

Still, the Padres have greatly missed Tatis’ presence atop their lineup. They've gotten little production in the leadoff spot since his injury, and they've been left searching for answers at third base as well.

Green offered no timeline for the rehab stint, and it's unclear how long Tatis might stay in Amarillo. He's spent the past couple weeks slowly working his way into game action at extended spring camp in Arizona.

"How quickly he returns will be dictated by how he performs and how he feels," Green said Friday.