KANSAS CITY -- During Royals rookie left-hander Kris Bubic’s MLB debut last week, he admitted that nerves got the best of him early.

Bubic had no such issue Wednesday night as he mowed down the first nine Cubs he faced at Kauffman Stadium, striking out four.

The Royals, however, lost, 6-1, extending their losing streak to six games.

• Box score

Bubic -- 22 years old and ranked by MLB Pipeline as the Royals’ No. 7 prospect -- certainly did his part, going six innings and giving up four hits and two runs. He walked two and struck out six while throwing 88 pitches, 52 for strikes.

Bubic's fastball command was spot on, and he got 20 called strikes or swings and misses on that four-seamer.

“For me, the big emphasis after my last game was to get that fastball command,” Bubic said. “So in the bullpen before the game, I really tried to get a feel for my body and my arm and release the ball in front of me.

“It’s funny that my curveball in the bullpen was pretty bad. First three or four were about 45 feet, and Salvy [Perez] couldn’t even block them. But it was good in the game.”

Bubic went to his curve early, 12 times, and got four swings and misses or called strikes.

“That curve,” manager Mike Matheny said, “turned out to be a plus pitch for him tonight.”

With his changeup -- Bubic’s best weapon -- he got six called strikes or swings and misses on 22 tries, though the pitch wasn’t good early on, he said.

The only damage Bubic permitted came in the fourth, and it came with some bad luck. Kris Bryant led off for the Cubs and punched a routine grounder through an open spot in the shift.

After a walk to Anthony Rizzo, Javier Báez floated a pop fly down the right-field line -- Báez was so unsure of where it was he didn’t even run at first. But the Royals had Báez played to pull, and the ball landed inches fair and far away from any defender, scoring a run and sending Rizzo to third.

A double-play ball by Willson Contreras plated the second run.

“It was an unlucky inning for me,” Bubic said, “but one thing I noticed was that I got behind in the count more often. The first three innings were somewhat of a breeze. I didn’t waste too many pitches. But against a lineup like that, second time through the order was a little tougher.”

Bubic needed 27 pitches to get through the fourth. But Matheny raved afterward about how Bubic fought through trouble.

“A good sign of what we’ve been so excited about,” Matheny said. “The way he carried himself in that fourth inning with a couple balls that found holes. It was a great start, and it was a shame we couldn’t get him more support.

“He would have gone longer than [six innings]. That was the only inning where the pitch count added up. It’s impressive.”

Once again, the Royals’ struggling offense couldn’t deliver a clutch hit.

The Royals had two on and one out in the second inning, but Adalberto Mondesi sent a 100 mph grounder that the Cubs turned into a 4-6-3 double play.

Maikel Franco doubled and Nicky Lopez singled to open the Royals’ third, putting runners at the corners. But a potential big inning fizzled when Whit Merrifield hit a sharp grounder back through the middle that Cubs starter Yu Darvish deflected. Second baseman David Bote made a terrific play to field the deflection while keeping one foot on the bag, then throwing to first for a double play. A run scored, but that was it.