Behind eight dominant innings of one-run, seven-hit work, Kennedy carried the D-backs to a 3-2 victory over the Padres at Chase Field.
"He's like he was last year, it looked like it," D-backs catcher Miguel Montero said. "He's more aggressive now. He was able to locate his secondary stuff, that was the difference in the game."
The win marked Kennedy's third straight after San Diego beat him on Aug. 25. Since that start, the right-hander has lowered his ERA from 4.44 to 4.08.
"He's pitched well, he's definitely had a better second half," D-backs manager Kirk Gibson said. "He's been more consistent. We made some adjustments from his last start against them. They were pretty rough on him."
Overall, Kennedy threw 121 pitches Tuesday, striking out six batters and walking two. Early on, however, it didn't appear he would last to the eighth.
Kennedy threw 30 pitches in the first and 19 in the second before finding a groove.
"I was falling behind trying to establish my off-speed stuff, I always say they are a very good hitting team," Kennedy said. "When that happens, you think you have to be real efficient as the game goes on. I was really happy Gibby let me go in the eighth. I felt pretty good. It's one of those things where you have to keep going."
With the victory, the D-backs remained 4.5 games back of the Cardinals, who also won Tuesday, of the second NL Wild Card spot with 15 games remaining.
The win also snapped a seven-game home losing streak to the Padres.
"They were playing pretty good, they've beaten a lot of people," Kennedy said. "They've taken care of us the last few times here. They are a good team."
While Montero helped guide Kennedy through his memorable evening, the catcher also led the club offensively, driving in two of the team's runs with a pair of two-out doubles off Padres starter Eric Stults, who shut out the D-backs over seven innings on Aug. 24.
"I was looking for a fastball, he made a couple mistakes and I took advantage," said Montero, who has reached base safely in his last 16 games. "For the most part, I was trying to just make good contact."
The D-backs returned Chris Young to the lineup on Tuesday after a 10-game hiatus, but the outfielder left after just one batter when he aggravated his strained quad making a running catch in right-center field.
"I put in a lot of work," he said. "But as soon as I got it, it grabbed on me."
After Young exited the game in the first, the Padres recorded their first run of the game when Yonder Alonso hit a sacrifice fly to left field, bringing home Logan Forsythe, who slid under the tag of Montero.
"They didn't hit the ball particularly hard in the first inning," Kennedy said. "But you have to scrap through it."
The D-backs didn't trail for very long, though.
After Adam Eaton set the table with a walk and a stolen base, Paul Goldschmidt drove in the tying run with a two-out single, and Montero put the club ahead for good, 2-1, with a double to right field.
Both pitchers settled down through the middle innings as the score remained the same until Montero delivered his second RBI double of the night, a shot off the center-field wall in the fifth to give the D-backs breathing room, 3-1.
"They had a little different approach," Stults said. "They were sitting more off-speed, especially early in the count. They were a little more aggressive."
J.J. Putz closed the door on the win in the ninth inning, recording his 30th save of the season.