WASHINGTON — He knew his 24th birthday would be better than his 23rd because, at this time last year, Nick Williams' baseball season expired. He was in triple A until the bitter end, stuck in a months-long slump that robbed him a chance to reach the majors. But, on Friday, he spent his birthday as the Phillies' cleanup hitter.

His assignment was Nationals ace Max Scherzer. Before the game, Williams met Matt Stairs in the batting cage underneath the visitors' dugout at Nationals Park. The Phillies hitting coach prepped his rookie outfielder with a warning: "This is probably the best pitcher you'll face in this league." They talked about a simple approach that has powered Williams since his promotion June 30.

He homered on the second pitch Scherzer threw him. It was the latest reminder of Williams' potential — and innocence.

"When I stepped in the box, the feeling, it was kind of crazy," Williams said. "You know? It's like a big-league call-up all over again when I stepped in the box. As a kid, you watch these guys do what they do. Then you actually step in the box against them. The result, that was crazy. I can't even explain it."

This Phillies season, with three weeks to play, is filled with more disappointments than surprises. Williams qualifies as one of the more shocking developments. He was hyped as a prospect because of his athleticism, but his detractors hedged on his lack of plate discipline. Then he came to the majors and improved his walk rate while cutting down on his strikeouts.

That is not a typical development.

"He has over 200 at-bats now, so he's really shown that he's improved," Phillies manager Pete Mackanin said. "That's the whole idea of the development process, making sure a guy is ready when he gets here. It certainly appears that he's made good adjustments."

In the dugout, Mackanin said the conversations about Williams always return to one realization: The rookie does not miss a pitcher's mistakes. Four of his five at-bats Friday lasted all of two pitches. That is fine; he recorded a hit on the second pitch four times. He has hit for average (.285) and power (an .839 OPS).

"Even when a runner is on first, I just want to get him in," Williams said. "Just thinking, 'Be short and move runners over.' That has helped a lot, instead of thinking about home runs. Thinking simple is panning out."

The dilemma is when to believe and when not to be conned by a few hundred at-bats. One hint, Mackanin said, to evaluate a young player by the caliber of pitcher he faces. He beat Scherzer in the first inning, struck out on five pitches in the third inning, then smacked a single in the sixth inning.

"To hit Scherzer like that gives you a good indication that he can handle the best," Mackanin said. "All in baseball, there's a lot of mediocre pitchers. So, do you hit the best guys?"

The front office has noticed.

"He has enough of a sample now that this is looks like the player Nick Williams is," Phillies general manager Matt Klentak said. "And that's not to say he can't get better. He's making improvements at the major-league level. Where some players come up and struggle and take steps back, he appears to be going the other way. He's been a very positive development success story."

Progress is needed on defense and the bases. Williams has overcome bad reads in the outfield with his speed. But he's shown cracks there. And, as a baserunner, Williams has committed mental mistakes. His instincts are not the sharpest. Sometimes, raw talent can rise above that.

The Phillies will keep challenging him. Williams has, so far, passed.

"The true test of a good player, a successful and winning major-league player, is the 162-game schedule," Mackanin said. "That's the true test."