With the win, the Dodgers pulled to within one-half game of the first-place D-backs in the NL West with three more games left in this series.
Penny (10-1) allowed just one run on four hits over eight innings to lower his league-leading ERA to just 2.04. If those numbers don't impress you, consider that Penny, who began his professional career in the D-backs organization, is now 7-2 with a 1.81 ERA in 14 career starts against the Snakes.
That was why the Dodgers changed their rotation and had Penny pitch in Arizona on Monday rather than against the Devil Rays on Sunday.
Penny hit 101 mph with his fastball at times, according to the Chase Field radar gun, and his split ran down and away from the right-handers. It was a pitch the D-backs saw occasionally when they faced him earlier this year, but he didn't throw it as often or as well as he did this time.
"That new split-finger pitch that he's got is definitely a good pitch for him," said first baseman Conor Jackson, who managed to get two of his three hits off Penny. "Before that, he was a fastball, 12-to-6 curveball kind of guy. Throwing that new pitch adds to his repertoire, and it makes him a better pitcher and tonight it showed."
Arizona starter Micah Owings held his own against Penny through the game's first five innings and actually held a 1-0 lead after Chris Young laced a rare Penny mistake off the wall for a two-out double that scored Jackson from first in the fourth.
Arizona had runners in scoring position in the first and second innings, but Penny clamped down when needed.
"The way he's pitching, it almost surprises you that you drive a ball and knock a run in," D-backs manager Bob Melvin said. "Just a tough guy to solve again."
Owings (5-2) allowed just two hits through five, but danger was just around the corner for him as he entered the sixth having thrown 72 pitches. Coming into the game, Owings had held the opposition down for his first 75 pitches, but from pitches 76 to 90 he allowed a .342 opponent's batting average, and that figure jumped to .385 from pitches 91 to 105.
"I'll look at it, but I felt good tonight and felt like I could have gone further, and even when I came out, I felt good and was disappointed that I came out," when asked if he tires later in games.
Penny led off the sixth with a double to left, and Owings got a bad break when Rafael Furcal hit a tapper so softly to the left side of the mound that he was able to beat it out for a single to put runners at first and third.
Owings then got Juan Pierre to hit a one-hopper at shortstop Stephen Drew. It looked like if Drew had fielded the ball cleanly, the D-backs could have turned two, but the ball came up on him and hit off his chest and rolled away for an error as Penny crossed the plate.
"It's a tough play if he makes it, but it's one of those smother ones where if you stay back, you're not going to get to [it]," Melvin said. "If you go get it, it's your only chance, and it's a tough play."
Owings is known for his mental toughness, and he displayed it when he followed the error by getting Nomar Garciaparra, who led the NL with a .429 mark with runners in scoring position, to pop out and Jeff Kent to fly out to shallow center.
With Owings one out away from getting out of the jam, former D-back Luis Gonzalez lined a 2-1 fastball to right to score the inning's second run, and catcher Russell Martin crushed a triple to right-center to score two more and give the Dodgers a 4-1 lead.
"It was frustrating because I had the two outs," Owings said. "The one pitch I didn't execute was the last pitch to Martin. I tried to triple up on my slider and left it a little out over the plate."
With the way Penny was pitching, that was more than enough offense, but the Dodgers tacked on one in the eighth and three more in the ninth for good measure.
It's hard to call any game or series a must-win in June, but with a 1-5 mark against the Dodgers, a team the D-backs figure to battle along with the Padres for the next three months for the top spot in the NL West, the next three games have a certain importance, even if it's just for Arizona's collective psyches.
"There's a lot of year left," Jackson said. "But with the Dodgers, they've always seemed to be our rivals in the west, them and San Diego, and we need to come out and show we can play with them so when September comes, we're comfortable in our situation ... because I know we play them a bunch and we play San Diego a bunch come September, and I think that's what it's going to come down to."
The good news for the D-backs is Penny won't pitch again this series.