The move, made necessary by the activation of pitcher Shawn Hill off the disabled list, is retroactive to April 14, when Lo Duca was hit on the right wrist with a pitch by the Braves' Jeff Bennett.
"I can't play right now," Lo Duca said. "I'm setting back the team. Maybe in three, four or five days I'll be able to go and get some at-bats in the Minor Leagues."
Lo Duca said he's in a situation that he finds very difficult.
"Stinks, really," he said. "Hopefully it gets better in 10 days or so."
Lo Duca suffered soft-tissue bruising on his right wrist. For the past three days, the Nationals' catcher has tested his readiness by hitting off a tee. Each time he has felt a sharp pain.
Lo Duca seemed optimistic before Friday's test, saying he was "hoping it would change a little bit." But he returned to the clubhouse shortly thereafter, flipping his bat down in disgust.
Wil Nieves started for Lo Duca in the Nationals' 14-inning loss to the Mets Thursday night in New York. Johnny Estrada got the start Friday night.
Nationals manager Manny Acta said that he was not surprised at Nieves' slick defensive work in the marathon game against the Mets.
"He's always been a great catch-and-throw guy," Acta said. "And he helped that the kid [John Lannan, who had 11 strikeouts] through a tough lineup. He plays with a lot of energy. He shows the pitchers the confidence he has in himself. The pitchers can tell he wants it. He's not afraid to block a ball or do what it takes."
In the next breath, though, Acta said he was looking forward to getting Lo Duca back in the lineup, because the Nationals had lost 12 of their last 13 games before Friday's 6-4 win.
"We need him because we need to get going," he said. "Actually we need a few guys to get going. But he's a big part of our club. We need him out there."
Acta said he expects Lo Duca to be fine eventually because a scan showed that nothing is broken.
Lo Duca seemed particularly glad to be in South Florida because a touted three-year-old horse he co-owns with former Major Leaguer Rob Murphy is at nearby Calder Race Course and Lo Duca plans to visit him in the barn early Sunday morning.
The owners have decided that they would "probably not" enter Golden Spikes in the upcoming Kentucky Derby, Lo Duca said. He noted that they are considering the Preakness Stakes, the second leg in the Triple Crown, or the Lone Star Derby in Texas or the Peter Pan Derby in New York.
The veteran catcher understands quite well that baseball makes it all happen for him, affording him the opportunity, among other things, to have the side thrill of owning a big-time racehorse.
"I'm trying to get back out there as soon as I can," he said.
Charlie Nobles is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.