Japanese baseball officials have been criticized for introducing a new ball this season without notifying players.
With nearly 60 games already played, Nippon Professional Baseball acknowledged this week for the first time that a new ball was being used. The new, livelier ball has resulted in more home runs.
NPB had previously denied this year's increase in home runs had anything to do with changes to the baseball.
"There was absolutely no intent to hide the truth," NPB commissioner Ryozo Kato said Wednesday. "We are sorry for any inconvenience we have caused."
An NPB spokesman said the balls used last season did not meet certain standards and the new balls were introduced to conform to the rules.
Many players criticized the practices of NPB.
"We had an idea something was different this season," Rakuten Eagles catcher Motohiro Shima said Wednesday. "Here we are almost 60 games into the season and now they tell us? It's very unfortunate. If they stay with the new ball or go with the old ball, it is problematic at this point of the season."
Before the 2011 season, different balls were used by the Pacific and Central Leagues. In 2011, NPB introduced a uniform ball to meet international standards.
In the 2011 season, there were 939 home runs and 881 in the 2012 season. The number of home runs in the current season stood at 512 as of Tuesday, on pace for a season total of 1,297.
"Just my personal opinion, but that we are even having this discussion about the ball is embarrassing for Japanese baseball," said Yomiuri catcher Shinnosuke Abe.
Following the announcement by NPB, Kyodo news agency reported that a Mizuno spokesman said, "We are going to let NPB take the lead on this. At this juncture, we are not prepared to comment."