KANSAS CITY -- The fear of Julio Rodríguez heading to the 10-day injured list with a lower back strain is now a reality for the Mariners.

Rodríguez underwent testing on Friday afternoon prior to the start of a three-game series against the Royals at Kauffman Stadium, and he landed on the IL at the most crucial time of the season.

“He’s still a little bit sore today,” manager Scott Servais said prior to his team's 5-1 loss. “It’s on his right side, top of his buttocks area. We’ll see how the findings turn out and go from there.”

This is a major blow for the Mariners, whose lead for the third AL Wild Card spot dipped to three over the Orioles with their 6-0 win over the Astros. Seattle, which also sits 1 1/2 games back of Wild Card co-leaders Toronto (84-67) and Tampa Bay (84-67), has lost six of its past eight games.

“You never know when a player goes on the IL if he’ll be ready to go off there after the 10 days, but all of our trainers and medical professionals think that he’ll be OK at that point,” Servais said after Friday's game. “Not only has he had a fantastic year, but he does so much for our team with his energy and really leading the charge for our team.”

Rodríguez’s pain seemed to begin last weekend in a road series against the Angels and then he left Thursday’s game vs. the A’s in the second inning, although the American League Rookie of the Year frontrunner initially wasn’t sure what caused the injury.

“I would say, it’s September,” Rodríguez said at that time. “That’s my best answer to it.”

In a corresponding move, outfielder Taylor Trammell was recalled from Triple-A Tacoma. He has hit four home runs to go with 10 RBIs and 15 runs scored in 41 games this season in the Majors.

Rodríguez is batting .280 and slugging .502, with 24 doubles and 27 homers this season across 129 games. On Sept. 14, he became just the third rookie in AL/NL history to put up a 25-homer, 25-stolen base season -- and he did it in three fewer career games (125) than Mike Trout (128).

Among AL rookies, Rodríguez currently ranks first in home runs (27), second in RBIs (73), first in total bases (251), second in stolen bases (25) and first in bWAR (5.7).

His impact on this Mariners team can't be overstated as Seattle is 9-12 without Rodríguez in the lineup this season and 73-56 with him in it. The 21-year-old leads the team in average, slashing .280/.342/.502 (.844 OPS).

This comes at the same time that their leader in home runs and RBIs, Eugenio Suárez, is also on the 10-day IL (right index finger fracture). Suárez appears to be ready to come back once the road trip concludes this weekend.

“Geno looked great today,” Servais said. “I was surprised with how hard he was swinging and letting it go. He should take BP tomorrow.”

It was Cal Raleigh who provided the only source of offense against the Royals in the series opener -- hitting his 24th long ball of the season, a Statcast-projected 396 feet to right field in the second inning. The Mariners have scored just one run five times in their past seven games.

“Baseball season is a long year and you’re going to have some ups and downs,” Servais said. “We haven't played well on this road trip, no question. We’ve won a couple games when we’ve come out and scored and when we don’t, it’s been one run. You’re not going to win 1-0 on the road.”

The earliest Rodríguez can return is in the final series of the regular season against Detroit. The timing is unfortunate with a playoff berth in reach, and it feels like the Mariners are trying to will themselves into the postseason and end a drought over two decades in the making.

“Things happen and this is when we find out, as a team, you don’t have to try any harder. But we’ve got to have good at-bats, really come together as a team and get it over the hump,” Servais said. “We’ll come out and play a really good game tomorrow, but tonight, I was disappointed we didn’t do more offensively because we had some chances early in the game.”