Players described it as similar to the loose soil used with potted plants, and it caused more headaches when an all-star team came over for a postseason tour in 2004. Roger Clemens’s foot was sore and Dontrelle Willis developed pain in his back, Cook said, because they were sliding more than usual on the pitchers’ mound.

Cook was camping with his family in the Blue Ridge Mountains when the league summoned him to Japan in an emergency.

“They were all complaining about how soft the mounds were,” Cook recalled. “I said, ‘Well, we can fix that.’ I came over and whipped up a concoction that got them through the rest of that tournament.”

Since then, the league has taken greater steps to ensure that Leake’s experience is the norm. Cook estimated he had been to Tokyo four times since the games were announced last spring. In between, he spent time in London, Mexico, New Zealand, the Dominican Republic and Peru — among other places — to work on fields for games, clinics and other events over the past year. His challenge is to ensure that wherever the game is taking place, the field is always up to M.L.B.’s competitive and safety standards.

There are plenty of other issues to address besides the dirt. For this series, Cook’s work began on March 4 and included helping lay a new, previously planned artificial turf surface at the arena. The bases used in Japan are also fluffier and rise to a crown, while American bases are harder and flatter. They also anchor into the base pits differently, so Cook not only has to bring bases from home but also has to change the holes into which they are fitted.

Japan also uses 12 permanent nylon markers — four around each batter’s box and four around the catcher’s box — as guides for laying chalk lines around those spaces; in the United States, a metal template is brought out before each game for the markings. In past events here, M.L.B. catchers complained that the half-inch-high tufts were distracting, and they would pull them out of the ground and toss them away. Cook now stores one of his metal templates at the Tokyo Dome, along with an array of other handy supplies.