Boone had earlier said that Loaisiga would start Thursday but clarified the order after the Yankees' 3-0 win against the Nationals.
"He's really talented, we think he has a very bright future," Boone said about Loaisiga. "His stuff is really good. He's a guy that pounds the strike zone."
Loaisiga is 6-1 with a 3.00 ERA and 58 strikeouts in 10 games combined for Double-A Trenton and Single-A Tampa this season. Other potential call-ups in Triple-A included Justus Sheffield and David Hale.
"Just getting to know [Loaisiga] a little bit this spring, we don't think he'll be overwhelmed pitching here at Yankee Stadium in the big leagues," Boone said. "We feel like his repertoire, his stuff will allow him to have a chance to be successful for us."
Boone said the 22-year-old Sheffield, one of the Yankees' highest rated prospects, remains in the mix for a call-up as he continues to develop in the minors.
The rotation replacement comes after Tanaka was hurt running the bases in Friday's win over the New York Mets at Citi Field. The right-hander strained both hamstrings tagging up from third and scoring a game-tying run in the sixth inning after batting at the NL ballpark.
Boone previously said Tanaka could be out for "weeks," although he mentioned Tuesday that the Yankees still aren't sure how many starts they would need Loaisiga to make. It could be one, two or even three, according to Boone.
Four hours before Tuesday's series opener against the Nationals, the right-handed Tanaka was out early playing catch for the first time since suffering the injury.