"As soon as I walked in, he said hi. And I was like, `Whoa, THE Roy Halladay,"' Johnson said Monday, the eve of their latest matchup.
Johnson's a big fan of the reigning NL Cy Young Award winner, despite being on the losing end when Halladay pitched his perfect game against the Florida Marlins last May 29. Tuesday's game will be Halladay's first in Miami since that night, and again Johnson will the opposing pitcher.
The latest duel between two of baseball's best pitchers ensures extra adrenaline in both dugouts, Phillies manager Charlie Manuel said.
"It's just natural," he said. "Everybody knows how good Johnson is. He's got a lot of respect around the league."
Johnson (3-1) led the NL in ERA last year and ranks second this season at 1.68 despite coming off his worst start of the season Thursday, when he lost at St. Louis. Opponents are hitting .160 against him, lowest in the majors.
Halladay (5-1) has a 2.19 ERA in seven starts and ranks among the major league leaders in strikeouts (57) and complete games (two).
While Johnson is 36-13 since returning from elbow surgery in July 2008, he figures he can learn a lot from his Phillies counterpart. When Halladay threw a bullpen session during a series against the Marlins early last season, Johnson received permission from the Phils to watch.
"Really, really impressive," Johnson, who at 27 is six years younger than Halladay. "He's one of those guys you want to model yourself after."
The two aces got to know each other better at last year's All-Star game.
"I was like a little brother to him," Johnson said. "I was following him around and trying to pick his brain about what he does between starts - little things I added into my routine."
Developing such a relationship should help both pitchers, Manuel said.
"They can not only learn - it builds confidence," he said. "And they also get more competitive."
Because of competitiveness, there are limits to Johnson's admiration for Halladay. The Marlins right-hander was in the clubhouse and not exactly cheering when Halladay completed his perfect game.
"It never really sunk in," Johnson said. "I watched the end of it, and as soon as the game was over turned the TV off."
Johnson went seven innings, and Florida lost 1-0 on an unearned run. He and Halladay combined that night for 17 strikeouts with only one walk.
The two other times they met, Johnson beat Halladay. The first matchup came in Johnson's rookie season in 2006, when the Marlins defeated Halladay's Toronto Blue Jays 4-1. The most recent meeting came in Philadelphia two weeks after the perfect game, when the Marlins edged the Phils 2-0.
In their three encounters, Johnson has allowed one earned run in 20 2-3 innings for an ERA of 0.43. Halladay's ERA is 1.96.
On Tuesday, Johnson said he'll be focused on what he's doing and won't pay much attention to Halladay. But he's looking forward to facing the first-place Phillies, who began the week with a two-game lead over Florida in the NL East.
"That's why you play - for the competition, to play against the best," Johnson said. "Although if you were to do it every time out, that might not be as fun."