"Firefly" star Nathan Fillion will have his hands full with two more competitors on his upcoming series "Drive."

FOX's midseason drama has signed on Kevin Alejandro and Mircea Monroe as co-stars in the chronicles of an underground race across the U.S., according to The Hollywood Reporter.

The two actors will replace the pilot's Andres Saenz-Hudson and Taryn Manning as race participants. Manning will likely stay with "Drive," but playing a different role.

This is just the latest substitution. Fillion replaced Ivan Sergei in the lead as the confusingly described "rogue landscaper."

The pilot's Alan Ruck and Shahine Ezell will also soon be replaced. The originals who've stayed on include Melanie Lynskey, Emma Stone, Kristin Lehman and Rochelle Aytes.

Fillion was last seen in the Sci Fi Channel's "The Lost Room" miniseries and as a guest star on "Lost." On the big screen, his credits include "Serenity," "Slither" and the upcoming "White Noise 2."

Alejandro currently guest stars as baby daddy Santos on "Ugly Betty" and is also known as Benny Velasquez from Showtime's "Sleeper Cell."

Monroe appeared on "Studio 60 on the Sunset Strip" and in "Cellular."