DETROIT -- Even the best rotations in baseball will go cold sometimes.
Exhibit A? The Tigers' losing streak, which reached four games after Thursday's 9-2 defeat against the Rangers at Comerica Park.
Robbie Ray, whose Major League career had gotten off to something of a dream start, became the latest victim, lasting just 3 1/3 innings and allowing seven earned runs.
Detroit starting pitching gave up seven runs for the second consecutive game, after Max Scherzer did it in seven innings of work Wednesday. The day before, Justin Verlander allowed five runs.
Tigers manager Brad Ausmus said a rough patch for a starting staff is an inevitability, even when you have the personnel that he has. Detroit still has the second-best ERA in the Majors at 2.98.
"There's not a team in the league that doesn't go through a stretch like this," he said.
Facing Yu Darvish, who entered Thursday with the third-best ERA in the American League, the deficit, which reached nine runs after the fourth inning, was far too large to overcome.
"For a pitcher, when you can't command the zone, normally that's going to make for a tough day," said catcher Alex Avila, who was removed from the game in the ninth inning to allow Bryan Holaday to catch Danny Worth. Worth became the first Tigers position player to pitch a full inning since Mark Koening did it in 1931.
Ray was sent down to Triple-A Toledo following the game, but the demotion had been scheduled to come earlier. Had Rick Porcello not needed a couple additional days to recover from side soreness, Ray wouldn't have made Thursday's start and would already be in Toledo. Ausmus said his curveball will be the focus.
"The breaking ball is certainly the No. 1 item on the list," Ausmus said following Thursday's game.
Ray had been dominant in his previous two starts, although the Rangers hit left-handed pitching far better than the other two teams he had faced in the Astros and Twins. Ausmus liked the way Ray commanded his fastball and changeup during his first stint with the big league club, especially in his first two starts. In those two outings, with Anibal Sanchez on the disabled list, Ray threw 11 1/3 innings and gave up only one run off nine hits.
Thursday, he doubled his hit total from his first two starts, and his ERA soared from 0.75 to 4.70.
"They were just hitting my mistakes," Ray said. "I was getting behind in counts, and they were taking advantage of it."
To replace Ray, the Tigers announced they will purchase the contract of right-hander Corey Knebel from Toledo. Detroit selected Knebel with the 39th pick in last season's First-Year Player Draft.
Though Ray, the 22-year-old rookie, held Texas scoreless in the first, the Rangers plated at least two runs against him in each of the next three innings. Darvish, meanwhile, threw seven innings of six-hit, two-run ball.
Ausmus tried to give his "taxed" bullpen a break by keeping Ray on the mound as long as possible, but he still had to turn the ball over earlier than he had hoped. Shin-Soo Choo hit a two-run homer in the fourth inning to make it a 7-0 Texas lead and forced Ausmus to go to the bullpen.
Picking up where Ray left off, Evan Reed allowed two more runs to cross the plate in the fourth off two infield singles and two walks.
Detroit got those two back, however, in the sixth inning when Torii Hunter and Miguel Cabrera led off with back-to-back doubles. Don Kelly later singled to score Cabrera.
Usual starter Drew Smyly entered the game in the seventh inning to mitigate the wear and tear on the bullpen. Smyly, whose next start hasn't been announced but could come as early as Monday, pitched a scoreless frame.
In the ninth inning, Ausmus saw the opportunity to give Worth a chance to try out his knuckleball that he has been practicing since he was about 10 years old.
Worth threw all knuckleballs with one exception -- a fastball that Chris Gimenez knocked for a single to center. He retired the next three batters in order, striking out two of them.
The Tigers have now lost four straight for the first time since May 28-31, 2013.
"I think regardless of the team, you're going to go through a stretch like this where maybe you don't get the starting pitching you think you're going to get and end up taxing the bullpen," Ausmus said. "It snowballs for a period of time."
Matt Slovin is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.