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.

Bubic — 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. The 22-year-old threw 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. With his changeup — Bubic’s best weapon — he got six called strikes or swings and misses on 22 tries.

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.

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 pitcher 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.