The New York Mets then plan to go to a six-man rotation with Matz and Syndergaard.
That lines up Jonathon Niese, Matt Harvey and deGrom for the showdown against the Washington Nationals that begins Monday in D.C. The Nats will counter with Max Scherzer, Jordan Zimmermann and Stephen Strasburg.
Collins could have used the struggling Niese against the Marlins on Sunday on standard rest and used Matz or Colon on Monday against Washington, but the manager said no consideration was given to doing so. Niese has a 9.92 ERA in his last three starts, including allowing six runs in five innings against the Philadelphia Phillies on Tuesday.
"This was set down a long time ago," Collins said about the pitchers facing the Nats. "I'm all done juggling all the pieces. I just told Jon last night when I took him out, 'OK, you've had a couple of bad outings. The next game is the biggest game you've ever pitched in your life. So get ready for it.'"
Meanwhile, the Mets decided to have Colon go on Saturday and Matz on Sunday against the Marlins for two reasons: Colon prefers pitching on standard rest, not with the extra day. This also allows the Mets to separate the left-handers, Matz and Niese, in future turns through the rotation.
Syndergaard is at 152 innings this season. That already exceeds his 2014 innings count by 15.