Cade Horton is now officially on the Chicago Cubs roster, the team announced Saturday. He will be available in relief for the scheduled bullpen game against the New York Mets, which Brad Keller will start.

[MORE: Cubs announce plan for Cade Horton, pitchers for Saturday game vs Mets]

In corresponding moves, left-handed pitcher Tom Cosgrove was optioned to Triple-A Iowa and right-handed pitcher Eli Morgan was transferred to the 60-day IL with a right elbow impingement. Morgan has not seen game action since April 15.

Cosgrove made his second appearance for the Cubs in Friday night’s 7-2 loss, allowing one earned run on two hits over two innings of relief.

[MORE: Cade Horton, Cubs No. 2 prospect, ready to make long-awaited debut]

Horton, who through six starts has the best ERA in Triple-A this season (1.24), is now readily available to make his MLB debut at Citi Field.

He will reportedly wear number 22 — the same number worn by Mark Prior, also a former first-round pick by the Cubs whom they developed into their top pitching prospect.

For that reason, the hype around Horton has drawn a lot of comparisons to Prior’s MLB debut in 2002, in which the latter struck out 10 over six innings in a win against the Pittsburgh Pirates.

Horton’s potential debut is coming under slightly different circumstances as the Cubs were forced to look to the bullpen to fill out what would have been Shota Imanaga’s start. Imanaga hit the 15-day IL Monday with a mild hamstring strain.

The 6:10 p.m. CT game will be nationally broadcast on FOX. Aside from Keller and Horton who did not pitch Friday, the Cubs will also have Porter Hodge, Chris Flexen, Daniel Palencia, Drew Pomeranz and Julian Merryweather available on multiple days rest. Gavin Hollowell and Ryan Pressly threw 21 and 19 pitches respectively in each of their innings of relief Friday.