"Bartolo's willing to do anything and he was great about it, but I'm not sure if I'm comfortable with his routine in that type of situation," Melvin said during a conference call on Wednesday. "We will see tomorrow.
"He's open for anything, but he does have a little different routine and I'm not sure how I'm going to handle that yet."
Melvin opted to go with rookie Sonny Gray as Thursday's starter, and if the A's can win it without using Colon, they'd be able to pitch him against the Red Sox in Game 1 of the AL Championship Series at Fenway Park on Saturday.
Either way, Melvin said Colon took Wednesday's news well.
"First of all, imagine how difficult it was for me," the skipper said. "This guy has 18 wins and has been our ace, and been as consistent as you could ever be. And he's an All-Star on top of it, 40-year-old veteran. He made it easy on me. He looked at me and said, 'OK, I just want a win.'
"He's a man of few words as it is, but it made the conversation difficult on me because he could have had a gripe, and I would not have been surprised if he did. But like I said, he made it easy on me and said, 'I just want to win.'"
So if not Colon, does Game 3 starter Jarrod Parker become available in relief?
That's debatable, too, since the righty made just 73 pitches before exiting Monday's victory after five innings. There's a sense Parker could be dealing with fatigue issues.
"Let's see how he is tomorrow," Melvin said. "He was sore after the game he pitched and we don't want him going out there when he's not close to 100 percent. I'm sure he will be willing to, because it will be an all-hands-on-deck-type situation, but we will have to see how he feels tomorrow."
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. Jeff Kirshman is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.