ST. LOUIS -- Entering the series finale against the Marlins on Sunday, the Cardinals were looking to complete a sweep while also reveling in the fact that the pitching staff they spent much of the offseason revamping was looking up, and a reinforcement was on the way.

Then, within an instant, a Cards staff that had been such a steadying force to start the season was hit with a jarring splash of reality.

What started with Kyle Gibson struggling to locate his pitches and surrendering two three-run homers in the first inning not only ended a seven-game, 37-inning spree in which Cards starters had compiled an impressive 3.16 ER, but also resulted in a 10-3 loss to the Marlins.

St. Louis’ rotation seemed to get a pregame boost when it was announced that Sonny Gray -- who was scheduled to start Opening Day before he suffered a hamstring strain in Spring Training -- would finally make his Cardinals debut on Tuesday against the Phillies.

However, those good vibes vanished in the first inning, when Jazz Chisholm Jr. and Nick Gordon blasted three-run home runs off Gibson, who had been stellar in his season debut vs. San Diego. Eleven batters into the game, the Marlins had a seven-run lead that propelled them to victory -- their first of the season -- and denied the Cards a sweep.

“I’ve always been told that you obviously can’t win the game in the first [inning], but you can lose it in the first and unfortunately I didn’t give my team a chance to win,” Gibson said. “Getting through six, sure [it was nice], but you want to be competitive in all six innings.”

Gibson, who resides in St. Louis in the offseason and had family in the crowd for his Busch Stadium debut as a Cardinal, was able to salvage the outing. By retiring 14 of the final 15 batters he faced, Gibson worked through six innings before the Cards called on their bullpen.

Even on a day when Gibson didn’t have his good slider -- which he relied on six days prior when he limited the Padres to two runs over seven innings -- he was able to find his rhythm over the final 4 2/3 innings of his outing.

“What he did was incredibly important,” manager Oliver Marmol said. “When you have an outing like that -- and you’re going to have them where it goes south early -- but your ability to make sure it doesn’t impact the next day is huge. For him to still give us six innings, that’s pro. It allows us to use two [bullpen] guys and be fresh for tomorrow because that’s going to be a big series.”

Gibson allowed the first two hitters he faced in the first inning to reach before he seemed to steady himself with a strikeout of red-hot slugger Jake Burger. However, Chisholm ambushed the first pitch he saw, a 90.4 mph cutter off the plate, crushing it a Statcast-projected 412 feet for a three-run homer.

After Gibson retired Jesús Sánchez, the Marlins got another big hit. Gibson got ahead in the count on Gordon, but the lefty drilled a low-and-inside curveball into the seats.

“I’d like to have the Gordon [pitch] back, because it was too much in -- because it needs to be farther down or farther away,” Gibson said. “But the pitch to Jazz, that’s where I’m trying to throw it. They hit some well-executed pitches there in the first inning.”

Before Gibson sat down with pitching coach Dusty Blake between innings and gathered himself for what would be a strong finish, Gibson allowed himself “a frustration moment” in the tunnel leading to the clubhouse.

“A little bit of everything, but try to be smart about it,” Gibson said when asked how he vents his frustration. “I love my glove, so I normally don’t throw that too much. And you never want to injure yourself when letting out frustration. So, there was a little bit of yelling and finding things that you can throw that won’t bounce back and hit you.”

Despite the rocky outing, Gibson thinks the Cardinals' have shown the potential they have in the season ahead.

“I think we have a lot of veteran guys who can execute pitches and work through a lineup,” he said. “Getting quality starts and working deep into games, you have to face their best hitters a third time. The only way you do that is executing pitches and a game plan. Hopefully that stability -- excluding today -- can be brought on a daily basis.”