If right-hander Dylan Cease didn’t know his seventh major-league start would have a different, more challenging feel than most of the others, the Astros let him know right away when George Springer hit his first pitch 467 feet into the left-field seats at Guaranteed Rate Field.

Granted, Cease had faced (and lost to) the Twins, the majors’ record-setting home-run-hitting outfit, two starts ago. But the Astros, World Series champions two seasons ago and a popular choice to win another in 2019, posed a boy-vs.-men test for Cease, 23, who’s getting his first taste of the big leagues.

Cease (2-5, 5.54 ERA) can be his own worst critic, and he did not give himself another passing mark despite allowing two earned runs (four altogether) in six-plus innings for his first quality start in a 6-2 loss in the first game of a doubleheader Tuesday. He walked five (one intentionally), gave up two homers and struck out only two.

“For me, it’s how I execute pitches, and I didn’t feel like I did it great today,” said Cease, unsatisfied with the command of his upper-90s fastball and the sharpness of his big curveball.

“I always judge my outings on that, not necessarily the results because those can be misleading.’’

Perhaps, but after Jose Altuve launched a 106 mph rocket into the left-field seats in the third inning, Cease retired the next 11 batters he faced, seven via the ground ball. Both unearned runs scored on passed balls by Welington Castillo, who had a rough game behind the plate.

Without talking to him first, manager Rick Renteria and Cease were unable to offer an explanation for Castillo’s misadventures.

The 32-year-old Castillo’s days with the Sox are numbered.

His contract is up after this season, and the way he’s performing behind the plate and with a .195/.267/.346 slash line in 50 games, it’s conceivable he doesn’t last the season. So for the Sox’ big picture, Renteria’s greater interest would be in Cease’s progress.

Cease, after all, is the future. The Sox are counting on him to be an important piece of their rotation next season, and perhaps a piece near the top. Renteria gave him a vote of confidence by intentionally walking Yordan Alvarez to load the bases in the first inning, and Cease responded by getting an inning-ending double-play ball off the bat of Yuli Gurriel.

“He’s getting better with every outing,” Renteria said. “Today was certainly a big one. [Pitching coach Don Cooper] was saying, ‘It’s a lot of confidence you showed when you walked to load the bases in the first.’ I have confidence in Cease, and he made a good pitch to get out of that inning. He’s got good stuff.”

Cease threw 98 pitches, 56 for strikes, seven of them swing-and-miss strikes. He avoided the big inning, a bugaboo for him in previous starts.

“As he learns to command and execute, he’s going to give himself a chance and put himself in a position where he gets deeper in ballgames,” Renteria said.

The Sox were in this one against right-hander Zack Greinke (12-4, 3.08 ERA), thanks to RBI doubles by Eloy Jimenez and Jose Abreu in the fourth and fifth innings.

The Astros pecked away with runs in the last four innings to pad the lead.

“I didn’t execute pitches that great, but we had a chance to win, so that was OK,” Cease said. “But it’s hard to be happy with a loss.”