KANSAS CITY -- It was one of those days when the White Sox knew they were in trouble even before their starter threw his first real pitch.

Right-hander Michael Kopech said he felt “a strain behind my knee” on his first warmup pitch when he took the mound for the bottom of the first inning on Monday afternoon against the Royals. He thought nothing of it.

“Second pitch, I felt it a little stronger” Kopech said. “I knew it wasn’t anything serious, but I didn’t want to make the third pitch stronger. So, I kind of softened through the rest of my warmups.”

What happened immediately thereafter put the White Sox in a steep uphill climb that would ultimately result in a 6-4 loss to Kansas City at Kauffman Stadium. Chicago's medical staff, along with manager Tony La Russa and pitching coach Ethan Katz, arrived at the mound to consult with Kopech. After taking a few warmup pitches, he told the assembly he was good to go.

But he really wasn’t.

Kopech faced four hitters while showing diminished velocity, and they all reached base. By the time Jimmy Lambert came in from the bullpen, the Royals led 1-0 and had the bases loaded with nobody out. Lambert allowed the first three hitters he faced to reach, and Kansas City found itself up 4-0 before the White Sox could record an out.

Kopech threw 19 pitches, and only nine were strikes.

“I continued to work around it the entire inning,” Kopech said. “I wasn’t going to be able to help the team today. The hard-headedness in me wants to stay out there as long as possible. But I wasn’t doing us any favors.”

La Russa decided to give Kopech an opportunity to work through the initial discomfort, but he was forced to turn to the bullpen four batters in as the White Sox saw reduced velocity from their generally hard-throwing right-hander.

“He threw some balls and said ‘no pain, no pain.’ So if you are feeling no pain and it doesn’t affect your arm, see what you’ve got,” La Russa said. “But you could see his velocity was down, so we didn’t push it.”

After the Royals got that significant head start, the White Sox huffed and puffed with a solid overall effort to pull even at 4-4 in the seventh inning. The bullpen held strong through the middle innings, and newcomer Elvis Andrus had a clutch RBI double that tied it en route to a three-RBI day.

But Joe Kelly hit the first two batters he faced in the eighth and later walked in the go-ahead run, with rookie Drew Waters getting his first Major League RBI.

“It’s a frustrating loss,” La Russa said. “We were down 4-0 and came back to tie it. We had some chances for one hit that would break open the inning."

The White Sox left 11 on base and had a run taken away in the sixth inning when a Luis Robert double to the gap in right-center bounced over the wall. Had the ball stayed in play, AJ Pollock would have scored. But he had to return to third and was stranded, symbolizing the type of game it was for Chicago as it tries to jump past the Guardians and Twins in the American League Central standings.

“You have opportunities and sometimes things don’t go your way,” second baseman Josh Harrison said. “We had a chance to win that game.”

Harrison lauded Kopech for staying on the mound following his pregame warmups and trying to work through the discomfort.

“He tried to gut through it,” Harrison said. “Unfortunately, he couldn’t. That’s part of a warrior bulldog mentality.”