Then came a mistake from Dodgers closer Takashi Saito. And with the way things have gone for McLouth these first two weeks of the season, he's not missing any mistakes.
The Pirates were down to their final out. McLouth was down to his final chance to extend a 12-game hitting streak. A one-run deficit was staring the Pirates in the face.
But with two runners on, McLouth turned on that 1-0 fastball from Saito, placed it rows up in the right-field seats and with it sent the Pirates out of Dodger Stadium with yet another come-from-behind win, this one 6-4.
"Nate did it again," said first baseman Adam LaRoche, who scored on the homer. "It's unbelievable."
After McLouth started the game 0-for-4, it didn't appear he'd have the chance to step to the plate to try to extend his hit streak. But after watching two different leads slip away on plays that helped to reiterate that baseball is a game of inches, the Pirates, with the same scrappy mentality they've been playing with all season, began to do it again.
With one out in the ninth, Jose Bautista, who had given the Pirates an early lead with a two-run, second-inning homer, extended the count full against Saito during an at-bat that included laying off one borderline pitch. He then took the sixth pitch of the at-bat and scooted it through the left side of the infield for a single.
A strikeout to Luis Rivas followed, before manager John Russell summoned LaRoche off the bench to pinch-hit.
LaRoche had been kept out of the lineup for the second straight game with the flu, and even though he took batting practice with the team prior to the game, as the game progressed, he hadn't.
"I got worse as the game went on. I was hoping to be able to come out to the dugout for the second half of the game, but when I laid back down in here, the cold sweats and everything started coming back," LaRoche said. "I was back here to the ninth with cold rags on my head."
But at the start of the ninth, he began putting on his cleats -- just in case. Then he got the call to face Saito, a pitcher whom LaRoche had never faced.
He took a first-pitch fastball and singled to center, for just his fifth hit of the season.
Up stepped McLouth, who entered the game with 11 RBIs and a number of big hits already this season. He was looking fastball all the way. He got one right down the middle.
"I have to guess that was probably a mistake because he has very good stuff, obviously," said McLouth, who, with the three-run homer, has already surpassed his RBI total from a year ago. "I was looking fastball, and I got it. It's a great way to kick off a road trip."
Closer Matt Capps then took that 6-4 lead and sealed it with a 1-2-3 ninth inning to pick up his fourth save of the season.
"Nate's been pretty much the catalyst of our club," Russell said afterward. "Everybody that came up that inning did a nice job."
After Monday's game, the Pirates have now had six of their 13 games decided in the final at-bat. Pittsburgh has come out ahead on three of those six games.
"That's the type of club we are," Russell said. "Our starting pitching is going to keep us there. Our bullpen is going to keep us there. Everyone is really pitching in."
Though it took until the ninth for the Pirates to put the big dent on the scoreboard, they had seemed poised throughout the night to break out against Dodgers starter Hiroki Kuroda. They connected for a number of hard-hit balls and knocked the Los Angeles righty around for seven hits in six innings, but managed to put just three runs up against him.
Bautista's homer accounted for the first two before Xavier Nady drove in Ryan Doumit to break a 2-2 score in the sixth.
In the meantime, Pirates starter Zach Duke was battling. Not only was he facing a club that the Pirates had beaten only four times in their last 18 games, but the left-hander was doing so without his best command.
"I was very inconsistent out there and my location was off," said Duke, who came into the game still searching for his first win of the season. "I felt like I had to rely totally on my sinker there for those first four innings. And then that sinker got up there a little bit in the sixth."
After the Dodgers had tagged him for an unearned run in the second without getting a ball out of the infield, they got Duke for another run in the fifth in part benefiting from a number of close calls. They tied the game at 2 in the fifth when Nady couldn't make a catch at the wall, resulting in a triple for Andruw Jones, and Kuroda followed with a double that bounced just inside the third-base line for his first Major League hit.
And though Duke would finish the following inning, he would give up two runs -- and the Pirates' lead -- in the sixth. However, to his credit, he kept the game within reach.
Down by only one, Russell called on the most dominant arms he has in the bullpen to keep it that way. John Grabow and Tyler Yates, who have given up just one run in 18 2/3 combined innings this year, each responded with a scoreless inning.
"I felt like the way we were swinging the bats, we were going to get some guys on," Russell said. "You want to keep the game as close as possible and those guys have shut the door for us all year, and they gave the offense the opportunity to come up only one run down."
And they gave McLouth yet another chance to shine.
"Not only is he hot, but he's getting the big hits," LaRoche said. "It's not going to last all year, but we're going to ride his bat as long as we can."
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.