CHICAGO -- All Chris Flexen could do was shake his head.

And after watching Cubs right fielder Nelson Velázquez’ go-ahead grand slam drop into the raucous left-field bleachers, Flexen’s reaction said it all.

The Mariners, on a day where things looked so good, so promising, early, saw things quickly turn south and go so, so wrong in a 14-9 loss to the Cubs at Wrigley Field on Tuesday. Velázquez’s big swing in the third inning capped off a massive Cubs comeback, erasing the 7-0 lead the Mariners held after 1 1/2 innings.

“It stings,” catcher Cal Raleigh said. “Obviously, we came out swinging it good, and took a big lead and couldn’t hold it. That’s baseball, that’s how it goes sometimes.”

According to ESPN Stats & Info, the Mariners are the first team since Sept. 27, 2001, to take a seven-run lead by the second inning and trail by the end of the third.

Seattle got off to a fast start against Hayden Wesneski, taking advantage of the young Cubs starter to the tune of five hits, four walks and seven runs (two earned) to end his night after 1 1/3 innings. But the Cubs responded by jumping all over Flexen in the bottom of the third, scoring eight times as 13 batters stepped to plate. At one point, nine straight reached base.

“When we got to the ballpark today, we knew the conditions were going to be very favorable for the offensive side,” said manager Scott Servais of the unseasonably warm, 76-degree April day on the North Side. “I thought early in the game, our at-bats were great. We jumped all over their starter, we were in a really good spot. Flex just didn’t have it as far as staying after it and on the attack. He got behind in some counts, he made some mistakes and the game flipped on us there in a hurry.”

Flexen, who was making his second start of the season, surrendered 10 hits and two walks and was charged with eight earned runs -- tying a career high. His 2 1/3-inning outing marks the second-shortest start of his career.

“It's very disappointing,” said Flexen, who joined the rotation after Robbie Ray went on the injured list. “The guys jump on a lead like that, and to not be able to hold it in that short amount of time is pretty embarrassing. I’m very frustrated, very disappointed.”

Flexen said he was not affected by the Mariners’ long second inning on offense, and had ways to stay loose as Seattle sent 10 hitters to the plate, scoring five runs.

And while the Cubs kept finding holes against the Mariners defense leading up to Velázquez’ plate appearance, Flexen also fell behind in several counts and had to work his way back over the plate.

“You have to stay on the attack, certainly, pitching on a night like tonight when the wind's blowing out, it's warmer, the ball is jumping,” Servais said. “You fall behind in a count where you walk anybody, it's gonna come back to bite you, and that's what it did tonight."

Said Flexen: “I was behind a handful of times. It felt like every hit just found a hole and I couldn't capitalize on the big out. They capitalized on the big hit. Couldn't limit damage.”

Tuesday was the 12th game of the young season for the Mariners, and just one out of the 162 they’ll play over the course of six months. But it was also the latest disappointing result for a team that has had an uneven start to a season with big expectations -- and the third straight.

Seattle lost 7-6 to Cleveland in 12 innings on Sunday and 3-2 to the Cubs in 10 innings on Monday in a series opener featuring missed chances and miscues.

“Yeah, it's frustrating, especially after such high expectations coming into this year and how excited we were and how well we played in the spring,” Raleigh said. “We’re not playing well right now. That’s the bottom line.

“We know it’s not going to last. We know we’ll start getting it rolling and things start clicking and things will start falling our way. That’s just kind of how baseball is.”