On Monday, he was a little of both.
There was dominance, as evidenced by the lively fastball and biting slider that led to a season-high-tying nine strikeouts. There was disappointment, as evidenced by the three balls blasted into the bleachers.
"It was an all-or-nothing kind of day," said Johnson, who gave up four runs on eight hits over five-plus innings.
Ultimately, however, it was a satisfying night. Nearly 24,000 celebrated career win No. 298, made possible when the Giants picked up an 11-7 victory over the visiting Nationals on the strength of a well-rounded attack that got a tide-turning boost from the blustery conditions at AT&T Park.
Randy Winn and previously struggling Travis Ishikawa each had three of San Francisco's 14 hits. Aaron Rowand doubled twice and drew two of the team's seven walks. And closer Brian Wilson put Johnson's third win of the year into the books by striking out Josh Willingham, the defensive goat of the game, to quell a ninth-inning uprising and pick up his eighth save.
"It's great for him and it's great for the Giants, so we embrace it," Wilson said of Johnson's march to the milestone. "It's fun doing the countdown, and it'll be fun celebrating with him."
Johnson didn't sound like he had a great deal of fun on the mound Monday, lamenting the mistakes he made against the persistent and powerful Nats, who hung around like, well, gnats.
Ryan Zimmerman was particularly hard on him, extending his hitting streak to 29 games with a single in the first inning that kicked off a 4-for-5 night with two homers, including a three-run shot in the ninth.
But Johnson certainly enjoyed the support he received while the Giants won for the 14th time in their past 20 games, moving a season-high three games over .500 and four games behind the first-place Dodgers in the National League West.
"Everybody had a great game, offensively and defensively," Johnson said. "Things are starting to click a little bit."
The defensive support Johnson received included a sensational second-inning catch in foul ground that took first baseman Ishikawa over a railing and tumbling into the seats down the right-field line.
"I really couldn't tell you how it happened," Ishikawa said. "It started off a pretty good way into the stands, but the wind was howling and brought it back."
That same wind helped the Giants build the 8-2 lead that their bullpen nearly blew.
Willingham whiffed on a routine fly ball to left field with two out in the fifth, leading to five unearned runs. Nationals starter Daniel Cabrera unraveled immediately after the error, issuing four consecutive walks (one intentional) before being replaced by Logan Kensing, who promptly walked in another run.
"We've seen it here before, the winds wreaking havoc," San Francisco skipper Bruce Bochy said. "It's a tough outfield to play. That's not the first time we've seen it, and it won't be the last."
It wasn't the first time the Giants have seen Johnson taken deep this year, either. If Monday was an all-or-nothing outing, his previous six starts were hit-and-miss.
In the two performances that brought him to Monday sitting on 297, Johnson allowed a total of four hits and two walks without surrendering a home run while striking out 16 over 14 shutout innings.
"He still can strike people out," said Nationals manager Manny Acta. "He showed that today. He's got that nasty slider, and he's tough on lefties and righties. [He has] deception and intimidation. He's obviously still got it out there."
Not every time out, though. In the four ho-hummers heading into the opener of this three-game series, Johnson looked every bit of his 45 years, giving up a total of 20 earned runs on 20 hits -- including seven homers -- while walking 14 over 17 2/3 innings, twice unable to get through the fourth inning and only once getting past the fifth.
"I don't get away with as many mistakes as I once did," Johnson conceded.
Moments earlier, he'd poked fun at himself for having already allowed 10 home runs.
"I'm on pace to catch Barry [Bonds] in [single-season] home runs -- giving them up, that is," he said. "It's a little frustrating."
But big league ball is a bottom-line business, and with another win Tuesday the Giants will secure the series victory and stay unbeaten (7-0-2) in their past nine sets. With wins in his next two starts, Johnson will be celebrating No. 300 in Seattle, where his life in big league ball began.
Ishikawa was born in the Emerald City and said he was in the stands at the Kingdome on Sept. 27, 1997, when Johnson posted career strikeout No. 2,000. Ishikawa was 14 at the time, and he still speaks of the Big Unit with child-like reverence.
"He's done so much for the game, it's incredible," he said. "I've never been a part of anything like [the quest for 300]."
The quest, however, is less important to Johnson than what he says is his top priority: winning games for the Giants and helping them catch and pass the rival Dodgers.
If winning a game in Seattle helps in that regard, great. If it's not win No. 300, so be it.
"I don't play those kinds of games in my mind," Johnson said. "I don't want to get that far ahead of myself. My next start is against the Mets on Saturday, and I think I'm facing Johan Santana.
"That's where my focus has to be."
Mychael Urban is a national writer for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.