Lucas Giolito is officially on the Nationals’ roster. (Jonathan Newton / The Washington Post)

The Washington Nationals officially have added top prospect Lucas Giolito to their roster, selecting his contract from Class AA Harrisburg to set the stage for his highly anticipated major-league debut against the New York Mets Tuesday night at Nationals Park.

To make room on the 25-man roster, the Nationals optioned reliever Rafael Martin to Class AAA Syracuse, and they released right-hander Taylor Jordan to create a spot on the 40-man roster for Giolito.

Giolito, 21, will take Stephen Strasburg’s turn in the rotation. Strasburg was placed on the 15-day disabled list because of an upper back strain Sunday.

Giolito was scheduled to pitch for Harrisburg on Monday but was scratched when the parent club chose him as Tuesday’s starter. Tuesday will be his first outing since he allowed five runs in 4 2/3 innings for Harrisburg on June 22. In his previous eight starts, the 16th pick in the 2012 draft had posted a 1.70 ERA in 47 2/3 innings.

Martin, 32, was called up Monday for temporary bullpen depth and pitched a scoreless ninth inning to finish Washington’s 11-4 win over the Mets.

Jordan, 27, made three starts for Syracuse and recorded a 1.72 ERA before it was announced that he would undergo a second Tommy John surgery and miss the remainder of the campaign. Jordan opened the 2014 season in the Nationals’ starting rotation but struggled. He went 1-8 with a 4.48 ERA in 94 1/3 innings for the Nationals across three seasons.