WASHINGTON (AP) – The Big Unit had to wait on Mother Nature, even with history on the line.

Randy Johnson’s bid to become the 24th pitcher to win 300 games was postponed Wednesday night after a series of thunderstorms left the field at Nationals Park unplayable for Johnson’s San Francisco Giants and the Washington Nationals.

Because of the significance of the game, officials waited until 10:47 p.m. EDT – more than 31/2 hours after the scheduled 7:05 p.m. first pitch – before calling it a night. The game will be made up as part of a traditional doubleheader, starting at 4:35 p.m. on Thursday.

“The field is not playable, and that’s the reason we can’t play,” Nationals president Stan Kasten said. “We really tried. We were all trying to get it done, but at the end of the night, it’s not worth the risk to our players.”

Johnson is scheduled to pitch the first game of the doubleheader. Nationals rookie Jordan Zimmermann, also scheduled to start Wednesday, will start Game 1 for Washington. San Francisco’s Matt Cain will face Ross Detwiler in Game 2.

The signs were ominous from mid-afternoon, when the tarp was placed on the field before batting practice. It was removed during a break in the storms around 8 p.m., but it was soon put back on when weather radar accurately predicted the imminent arrival of another line of lightning, thunder and rain so dense that the Capitol dome was no longer visible from the upper deck.

At 10 p.m., Kasten predicted the rain would end soon and announced: “We are going to play this game.” But the rain kept falling longer than expected, and shortly afterward Kasten and the umpires were sloshing through masses of standing water in the outfield to see whether it was suitable for play.

Johnson was aiming to get win No. 300 on his first attempt. He got his 299th victory last week when the Giants beat the Braves 6-3.

Before the storms hit, discussions centered on whether the 45-year-old lefty will be the last to reach the milestone. Pitch counts, quick hooks and an overall abundance of caution with pitchers have made consistent big-win seasons a rarity.

“He’s going after a tremendous accomplishment that probably we’ll never see again,” Washington manager Manny Acta said. “It’s becoming tougher and tougher.”

Only four pitchers have averaged at least 15 wins over the last six full seasons, and the career leader among those four – Roy Halladay – has only 140 wins at age 32, putting him about a decade away from 300 at his present pace. The only contenders above 200 wins are 46-year-old Jamie Moyer (250), 36-year-old Andy Pettitte (220), 37-year-old Pedro Martinez (214) and 42-year-old John Smoltz (210).

“I think we’ll see it again. It’ll be a while,” San Francisco manager Bruce Bochy said. “Of course, there’s Moyer. He can pitch until he’s 50, I guess. The way bullpens have evolved in baseball, it makes it more difficult for these starters to get the decisions. They’re not in there when the game’s decided. Randy, if you look at his decisions, and the guys who have won 300, that’s one common denominator that they have. That’s why it’s going to be a lot more difficult.”

AP-ES-06-03-09 2330EDT