SEATTLE -- Clearly the biggest challenge with Major League Baseball’s shortened season falls on starting pitchers who must gear back up quickly following the 3 1/2-month shutdown.

For Mariners southpaw Yusei Kikuchi, that point was driven home by a rough intrasquad debut Tuesday. He walked four batters in 2 1/3 innings while giving up four runs on four hits.

The 29-year-old from Japan appears lined up to pitch Seattle’s second regular-season game on July 25 at Houston, but he’ll have just one more intrasquad game to get ready. The clock is ticking.

“I only have one more outing before it’s ‘go time,’ so I need to make my proper adjustments and get ready,” said Kikuchi, who was having a strong Spring Training in Arizona before baseball was shut down in March because of the COVID-19 pandemic.

• Mariners "need to be smart" with Kelenic

The second-year big leaguer is a workaholic, and he threw regularly during the downtime, but Kikuchi acknowledged it felt different getting on the mound in a game situation after the long layoff.

“My bullpens have been really solid lately, so I really felt a difference between the bullpen and actually pitching in a game,” he said through interpreter Kevin Ando. “It’s obvious there’s a lot more stuff going on -- signs, runners on base, tempo. So I kind of felt I lost my balance and mechanics.”

Kikuchi gave up a first-inning home run to rookie first baseman Evan White and then walked the bases loaded in the second before surrendering a two-run single to Shed Long Jr.. A leadoff double by Austin Nola in the third led to another run when Nola scored on a sacrifice fly by Tim Lopes.

On the plus side, Kikuchi was hitting 95 mph with his fastball and said his stamina and arm feel good, so now it’s a matter of fine-tuning his fastball command.

“I think they’re just minor tweaks, little adjustments,” he said. “I think I should be ready to go by Opening Day.”

Hirano goes on injured list
Right-handed reliever Yoshihisa Hirano, the only Mariners player who has yet to appear at Summer Camp, was placed on the injured list on Tuesday, though no reason was provided. The 36-year-old signed with Seattle as a free agent after going 5-5 with a 4.75 ERA and one save in 62 outings for the D-backs in 2019.

Major League Baseball has instituted a COVID-19 list this season, although clubs will not announce which players are placed on it because of privacy laws regarding individuals’ health. Players may address their status if they wish, though they are not required to do so. Merely being placed on an injured list without further explanation is not confirmation that a player has tested positive for COVID-19. For example, potential exposure to a person who has the virus can be sufficient cause.

Unlike the normal 10-day or 60-day injured lists, the COVID-19 list doesn’t have a specific length of time that a player must sit out. Any player who does test positive for COVID-19 must have two negative tests at least 24 hours apart before being cleared to return.

Time short for late arrivals
Center fielder Mallex Smith and utility man Dylan Moore -- two players initially expected to be part of the 30-man Opening Day roster -- will be in a tight squeeze to get ready in time for the July 24 opener at Houston. Both were cleared to join the team Monday.

Manager Scott Servais said those two, plus Minor League catcher Joe Hudson, will be limited to morning workouts for the next few days before likely making their intrasquad debuts on Saturday. No reason was given for the trio’s late arrival, but players must clear COVID-19 protocols before being allowed in camp.

Smith was pegged as the starting center fielder, though Kyle Lewis has been working in that spot the first week of intrasquad games. Once Smith is ready, Lewis likely will shift to right field or split time with Smith in center.

Moore is one of three utility players competing for roster spots, along with Lopes and Sam Haggerty.

“They have not been doing a lot of baseball activity here recently,” Servais said. “So we have to be smart in how we ramp them up.”

Short takes from T-Mobile Park
• White, who will open the season as the starting first baseman, joined the rookie power display with his first intrasquad homer. Fellow rookies Lewis (three) and Jarred Kelenic (two) have been the early camp standouts. Veteran third baseman Kyle Seager joined the power party with a blast of his own in the bottom of the first, a two-run shot off Nick Margevicius.

• Kelenic followed up his two-homer day Monday with an RBI single in his first at-bat Tuesday. He then flied out to center in his second plate appearance in the five-inning contest. He’s 5-for-8 with two doubles, two homers and three RBIs in four games.

• Lewis went 0-for-1 with two walks to put him at 3-for-8 with three home runs and four walks in his four outings.

• Kaden Polcovich, the team’s third-round Draft pick last month out of Oklahoma State, was a late scratch from the intrasquad game Monday. Fellow prospect Austin Shenton filled in for him at second base. Servais said Polcovich was just “dragging” from the recent workouts and needed a day or two of recovery.

• The Mariners likely will open the season with 17 pitchers on the 30-man roster, Servais reaffirmed on Tuesday, which means 11 relievers and six projected starters.