Speaking for the first time since a report in Monday's Tacoma News Tribune quoted an unnamed player saying Griffey "was asleep in the clubhouse. He'd gone back about the fifth inning to get a jacket and didn't come back. I went back in about the seventh inning and he was in his chair, sound asleep," Wakamatsu said that was not true.
Griffey told reporters on Tuesday that he was available to bat for catcher Rob Johnson and took a swipe at the unknown player who said Junior was sleeping while a game was being played.
"I hope that whoever said it is man enough to come to me," Griffey said.
None of Griffey's teammates had stepped forward as of late Tuesday afternoon.
"What I know is that he was not sleeping when that situation came up, and I know that for a fact," Wakamatsu said. "When you read stuff, the first thing you think is 'Is there any truth to it?' He was in the dugout. I said in my postgame press conference when asked if he was available ... I said 'yes.' He was not sleeping.
"There are things you read, and people associated with the team know what the truth is. My statement is he was available to hit and no, he was not sleeping. I know that for a fact.
"Griff is trying to pull up evidence now in the TV footage."
The Mariners had a players-only meeting Tuesday afternoon before the clubhouse doors were opened to the media.
Griffey met with the larger-than-usual horde of road media and basically took the high road.
"It is what it is, and I will just let it go," he said. "It's best for me to let it go and try to be as professional as I can be. It's my word against someone else's word."
Asked if he was disappointed that he was not given a chance to respond to the accusation before it became public, Griffey said, "I would rather let it go, move forward and be a man about it. That's the best I can do."
Johnson was among the players who went to bat for the 40-year-old likely first-ballot Hall of Famer.
"If anyone said that, I doubt that he's on the 25-man roster, and I think it's a lie," Johnson said. "I think everybody in this clubhouse loves Junior and would stick by him, just like he would stick by us.
"I don't think [the sleeping episode] was true. I would have heard about it, no doubt. There's no way most of us would not have heard about it. I just don't know where that could have come from."
Wakamatsu was asked after the game -- the Mariners' eighth straight loss -- if he thought about pinch-hitting Griffey for Johnson in the eighth inning with two outs and two on.
Johnson struck out against Angels right-hander Kevin Jepsen.
Wakamatsu used a similar situation in Sunday's losing-streak-breaking victory over the Angels as to why he didn't pinch-hit for Johnson.
"I had an opportunity to hit for [Adam] Moore, but I didn't, and he ended up getting a hit that might turn his season around. He gets a hit to right field and feels a lot better about himself, and that's after three strikeouts. All of a sudden his confidence level goes up."
The way the overall offense has gone this season, "I could pinch-hit for everybody," Wakamatsu said.
As for the Griffey issue, Wakamatsu said it was another example of various distractions that come up during the course of a season. "We deal with them and move forward. I don't think there's a problem in our clubhouse."
Griffey took about 10 minutes quietly discussing the controversy.
Later, he said, "I'm good, I'm fine. I always have fun and I told you from day one that when I stop having fun, that's when I will [retire]. That hasn't changed.
"It is what it is and people will believe what they want to believe. Oh well. You get over it."
Griffey went into Tuesday night's game with a .208 batting average, no home runs and five RBIs and was dropped to seventh in the lineup.
"This isn't a reactionary move," Wakamatsu said. "It is something we talked about before this article ever came out. I talked to Junior last week when we were home.
"It's not only him, but we're trying to juggle this every which way. Junior has said all along that he would do anything to help this organization."
Jim Street is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.