DUNEDIN -- Vladimir Guerrero Jr. is expected to miss the next three weeks, after he was diagnosed with a Grade 1 strain of his left oblique muscle.

Guerrero sustained the injury during his final at-bat of Friday's win over the Pirates. He will be shut down for the next week, and the hope is that Guerrero will return to the Minors, or to extended spring training approximately two weeks after that.

"In his last at-bat he felt a sharp pain in his side, which for the first time for any young player is a frightening feeling, and fortunately it is just a Grade 1 and it's something we'll be able to manage," Blue Jays general manager Ross Atkins said.

"He has a very aggressive swing, which is part of the reason. We'll be very careful and ensure that he is ready for that cage work, and there will be less rotational work for the next week."

Guerrero had four hits with one RBI in 19 at-bats this spring. He has been ruled out for the remainder of Spring Training, and likely should be expected to miss a couple of weeks in the regular season as well.

The 20-year-old third baseman technically was competing for a spot on the 25-man roster but all along the expectation was that Guerrero would start the year at Triple-A Buffalo. If the Blue Jays delayed his arrival in Toronto by a few weeks, the club would have gained an extra year of control, and this latest injury all but officially guarantees that will be the course of action.

Guerrero is the No. 1 prospect in baseball, according to MLB Pipeline. He slashed .381/.437/.636 across four Minor League levels last season. The injury is a disappointing setback, but one that Guerrero apparently has been handling OK.

"He's so upbeat and positive," Atkins said. "The most discouraging thing for him is that he's not playing in baseball games. He loves to compete. he loves to play and he'll see this as an opportunity to get better."