SAN FRANCISCO -- Randy Johnson threw a pitch to Fred Lewis that the radar gun couldn't get a read on.
It was too slow.
The suddenly slow tossing strikeout king tossed seven shutout innings to win his fourth straight start and the Arizona Diamondbacks completed their first sweep in San Francisco in seven years, beating the Giants 7-2 on Sunday.
The 44-year-old, who recorded career win No. 292, extended his scoreless inning streak to 15, his longest since 19 straight in September 2002.
"Over the years you change a little bit and this year it's more so than any," Diamondbacks' manager Bob Melvin said. "He's going to different resources but he's still a power pitcher."
The second-most prolific strikeout pitcher even threw a pitch so slow to Lewis in the first inning -- for a strike -- that the radar gun was unable to register its speed.
"I think it was a purpose pitch. It kind of shocked me," Lewis said. "And he threw it for a strike. There was no way I could hit that pitch."
Johnson (8-7) earned his first win in San Francisco since July 16, 2002. He allowed nine hits, struck out two and did not walk a batter.
"I've been around long enough to know you're going to pitch poorly at times," Johnson said. "It was frustrating to go through what I did in June. I was searching and wondering even as I knew it was still there."
Johnson returned to his alma mater at Southern California for a few days to watch film and get some throwing in.
"For me it's all about mechanics," he said. "I feel a lot more comfortable now and I'm making pitches when I need to make them."
Conor Jackson had three hits, including a home run for the NL West-leading Diamondbacks, who have won five of six to move two games over .500 for the first time since June 24. Mark Reynolds added a two-run homer and Stephen Drew drove in a pair of runs.
"I'm feeling good. There's nothing more I can say," Jackson said. "That's all I've got for you. I'm getting my pitch to hit and I'm taking advantage of it."
Lewis had four hits for the Giants, becoming the first left-handed hitter to get that many hits off Johnson in a game. Ivan Ochoa and Randy Winn each had two hits for the Giants, who have lost 12 of their last 16 games.
Barry Zito (5-13) became the first 13-game loser in the majors, giving up six runs and six hits in five innings. He walked five and struck out four in his fifth straight loss to the Diamondbacks.
Zito and Johnson, the 2002 Cy Young Award winners, were impressive through three innings. Arizona scored four times in the fourth, taking advantage of Zito's wildness.
Zito walked four in the inning, including Chris Snyder with the bases loaded. Tony Clark drove in a run with a groundout and Drew added a two-run single.
"I started to nit pick instead of being more aggressive," Zito said. "It's frustrating that I had a good approach the last couple of games and then I fell back into what I was doing."
Johnson allowed hits in all but the fourth but pitched around trouble. Only two runners reached third during Johnson's tenure.
Jackson, a former Cal-Berkeley star, is hitting .478 (11-for-23) in San Francisco this year with four home runs, nine RBI and 10 runs scored.
"I've never seen anyone as hot as him," Johnson said.
Winn scored San Francisco's first run when Aaron Rowand grounded into a double play in the eighth. John Bowker added an RBI single in the ninth.
Drew extended his hitting streak to 12 games. ... Zito received run support of one or less for the 11th time in his 21 starts. ... Rich Aurilia played in his 1,182nd game as a Giant, tying J.T. Snow for sixth on San Francisco's all-time list. ... Jackson's five home runs in San Francisco are his most in a road ballpark. ... The Diamondbacks last swept the Giants in San Francisco in a three-game set May 28-30, 2001. ... Lewis had four hits and stole two bases in a game for the second time in his career.