The Blue Jays' most valuable pitcher so far this season will undergo further evaluations on Tuesday morning, and there is no immediate timetable for his return.
Manager John Farrell did not want to speculate on how long Morrow could be out, but early indications do not sound positive for a quick recovery time.
"We'll get a better read on his condition after further tests are done tomorrow, but I think at this point, it's safe to say it's probably substantial in terms of what he's dealing with right now," a somber Farrell said after his club's 6-3 loss to the Nationals.
"Any kind of time length, there's really no read on that yet until we get the further testing, but it's unfortunate given how well he has been pitching and what he means to this rotation, this staff and, certainly, this team."
Morrow suffered the injury while throwing his first pitch to Bryce Harper, Washington's No. 2 hitter. Morrow threw two additional pitches as he tried to manage the pain, but quickly realized something was seriously wrong.
Toronto's No. 2 starter motioned to the dugout for assistant trainer Hap Hudson and Farrell. After a very brief conversation, he was removed from the game and headed straight for the clubhouse to undergo a series of tests.
"I felt like a stabbing pain in my side when I threw it," Morrow said of his first pitch to Harper. "Just put it out of my mind for the second pitch, just continued on like nothing happpened, and hopefully it [would be] nothing.
"I threw [the second] and felt the same thing, and then of course I was thinking about it for the third pitch and wasn't able to deliver the ball very well. We're calling it an oblique strain right now, and we'll know more tomorrow."
Losing Morrow for an extended period of time would be a massive blow to the Blue Jays' aspirations of reaching the postseason. The 27-year-old has established himself as the club's best pitcher while also ranking among the best the American League has to offer.
Morrow is 7-4 with a 3.01 ERA in 77 2/3 innings this season. He also has struck out 67 batters while walking just 24 to go along with a Major League-leading three shutouts.
"He has been a very consistent, very quality starter for us," Farrell said. "Each time he takes the mound for us, [he's] a guy that we have the utmost confidence in.
"Unfortunately, injuries are part of this game, and this is what we're dealing with right now. But because of his absence, our expectation, our level of expectation and what we still work towards accomplishing as a team does not change."
Morrow previously suffered a right leg injury when he was struck by a line drive off the bat of Baltimore's Wilson Betemit on May 30. Morrow did not miss a start and proceeded to record a shutout on 119 pitches in his next start against the White Sox.
The native of California didn't feel that his oblique strain had anything to do with the leg injury or the heavy workload that immediately followed. Morrow said he felt great in the days leading up to his start, his bullpen session before the game, and even when Steve Lombardozzi led off Monday with a double to the right-field corner.
The positive feelings quickly went away against Harper, and the Blue Jays now eagerly await Tuesday's news hoping for the best, but potentially hearing the worst.
"He continued to tighten up after he came out of the game," Farrell said. "He was in considerable pain. It's in the oblique area, right below the bottom rib on the left side of the rib cage, and that's kind of the classic oblique area. I know there will be further imaging first thing in the morning."