CINCINNATI -- First-inning struggles continue to plague the Mets as Kodai Senga coughed up four runs in the first frame of a 5-0 loss to the Reds on Thursday at Great American Ball Park.

It was the fifth straight game New York gave up a first-inning run -- and the eighth time in nine games -- as the Mets wrapped up a fifth straight series loss.

Senga’s outing raised the Mets’ first-inning ERA to 8.05, the second-worst mark in baseball behind the Reds. Worse yet, New York is dead last with just nine first-inning runs in 38 games, which has made for a lot of early deficits. The Mets have been outscored 34-9 in the first inning this season.

“When you’re not scoring runs, all of that gets multiplied,” manager Buck Showalter said. “Pitchers feel like there’s not much margin for error. It’s a tough mindset to pitch in.”

How bad is the Mets’ first-inning run problem? Consider these stats:

When they give up a first-inning run, the Mets are 4-13 this season. They are 14-7 when they do not. New York is 1-9 when giving up multiple first-inning runs.

The Mets have given up a first-inning run in just four of their 18 wins (five total runs). They have allowed a first-inning score in 13 of their 20 losses (29 total runs).

Senga nearly got out of the first unharmed before things really unraveled and the Reds batted around. Following Jonathan India’s leadoff double, the right-hander retired TJ Friedl and Spencer Steer on seven pitches. But the next five batters reached base as the Mets could not catch a break.

Jake Fraley broke the seal with an RBI bloop single up the middle, and Tyler Stephenson sneaked a soft grounder through the right side. Nick Senzel’s RBI double was well-struck with a 99.1 mph exit velocity, but Kevin Newman's bases-loaded single through the left side missed shortstop Francisco Lindor's glove by millimeters, scoring two runs to cap the frame.

“I think those weak hits turning into hits are just the result; it is what it is, and there’s not much you can do about it,” Senga said through a translator. “But after letting in those runs in the first inning, it’s hard to get the team in a groove. It’s something I need to work on.”

There are some natural challenges that come with pitching in the first inning. You’re automatically facing the top of the lineup and the team’s best players, and starters often aren’t yet in a groove. Take Wednesday’s win, for example, when the Reds crushed their three hardest-hit balls against Justin Verlander in the opening frame (all over 100 mph) and picked up an early run.

“Most starters are that way, especially the good ones,” Showalter said. “If you’re going to get them, you’ve got to get them early, kind of like Verlander. But the problem there, instead of one, it turned into four. And that was really the difference between [Senga’s] start and Justin’s start.”

The Mets’ early struggles have been a major factor in their current slide. Since April 22, they have lost 13 of 17 games, the worst mark in the National League during that stretch, and fallen from a half-game out of first place in the NL East to 7 1/2 games out and fourth place.

Including Thursday’s game, New York has been shut out four times during this stretch (seven times on the season), so it’s not as though first-inning scoring is the only issue at hand. But the Mets are well-aware that digging themselves into early holes has been one of the biggest problems holding them back.

“I definitely have noticed it for sure,” Lindor said. “It’s just a matter of going early. We have gotten behind a lot, or we just haven’t scored in the first inning quite a lot. As a team, we are doing everything possible to get going early and to continue to put runs on the scoreboard. We’re trying to win innings, we just haven’t done it as consistently as we wanted.”