"I would expect that we'll let you know tomorrow," MacPhail said before Sunday's series finale with the Yankees. "It's really just a function of the innings and what is best for the kid. Whether it's a good outing that he ends on or a bad one, it's really a mathematical equation."
Matusz, the fourth overall selection in the 2008 First-Year Player Draft, zoomed through the team's farm system this year and has pitched competitively through his first eight big league starts. The southpaw has completed seven innings in each of his past three starts and has a 5-2 record to go with a 4.63 ERA. In Saturday's 7-3 win over the Yankees, Matusz scattered four hits over seven innings, allowing the team with the Majors' best record just one run.
And while the Orioles are thrilled to let Matusz gauge his stuff against big league competition, they're also worried that they don't have any professional precedent in terms of his workload. Matusz, who is 13 months removed from signing his first professional contract, has pitched 157 2/3 innings between three organizational stops.
MacPhail has said several times that Matusz has moved quicker than he expected, and he has also repeated the team's need to be extremely careful with its top pitching prospects. Manager Dave Trembley has presided over that process, and he said on Sunday that the Orioles have to take a long-term approach with Matusz.
"First of all, I think you have to do the right thing no matter what, whether a guy is pitching good or not," Trembley said. "But I think it's a little easier if in fact you did shut the guy down that you leave him with the game that he had [Saturday]. That could be the swan song, so to speak.
"I always think you look at the whole body of work and the entire situation, and you base the decision on that. What's he thrown, 157 innings this year? I think we'll be OK with it."
Spencer Fordin is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.