And speaking of five ... that's how many home runs -- also a season high -- the Bucs powered in support of Locke's seventh consecutive winning decision.
Still, Locke was principally responsible for delivering the Pirates to a 20-year-high 17 games over .500 at 47-30.
And he did so despite what manager Clint Hurdle characterized as "his lightest stuff of the season."
"Not a lot of rhythm and rhyme early," Hurdle expounded. "He just went out and basically battled."
You have indeed come a long way when you allow three hits in the first two innings and it's seen as a struggle. That's the point reached by Locke, who allowed all of two runs in seven innings, which was enough to "balloon" his ERA to 2.06 and take him out of the league lead (second only to the Mets' Matt Harvey and his 2.05 ERA).
"He does a great job with his fastball," Seattle manager Eric Wedge said of Locke. "He widens the plate and pitches inside to both right-handers and left-handers and really drives it in there. He works his changeup off that, then toward the end of the game he started using his breaking ball more, which was really effective, too.
"You can see why he's had some success because he throws the ball where he wants to and uses all his pitches aggressively."
The Buccos batsmen made quick work of lefty Joe Saunders, muscling up for three homers in the second for a 6-0 lead, then got out of the way, turning the stage over to Locke.
Well, all but Starling Marte got out of the way. After tripling in the first and homering in the second, Marte got in a last word with another solo homer in the eighth to post his first career multi-homer game.
"I'm not focused on power," Marte said through interpreter Heberto Andrade, the Pirates' bullpen catcher. "I jut try to hit the ball hard. If it goes out, good. If it stays in, I try to go for the extra base."
Gaby Sanchez delivered the final salvo, off reliever Carter Capps in the ninth, of an outburst that carried a subtle message about the depth and potency of the Pittsburgh attack: Five home runs, and none of them by Pedro Alvarez, who had been on a homer tear compelling enough to earn him National League Player of the Week honors.
"The power jumped up, and it was nice to see. I felt confident it would come on this trip," Hurdle said.
Alvarez's only offensive contribution this game was the Pirates' 13th and final hit, a ninth-inning double which did stretch his hitting streak to nine games (14-for-37), within two of the career-high 11-game streak in his rookie 2010 season.
Otherwise, Locke commanded center stage the way he has for two months. His effort was routine, yet there was nothing routine about it.
In his seven innings, he allowed four hits and two runs, while walking two and striking out four.
This was Locke's 13th consecutive start in which he did now allow more than three runs. For the 10th time in those 13, he did not allow more than four hits.
"It makes you feel good," Locke said about putting up his usual pitching line without his usual pitching stuff. "It was fun to see the offense fire on all cylinders. It was good to get that offensive padding."
Locke's seventh consecutive win drove more nails into his platform for All-Star candidacy, yet his own manager downplayed his chances in a manner that only shed light on his instant stardom.
"He's got six wins this year -- and seven lifetime," Hurdle had reasoned before the game. "Keep it in perspective. I really think he's on the outside looking in. We can talk numbers all we want, and the numbers make sense. But in reality he is a very young, not many people know about him, other than the people he's pitched against."
The inset of the Pirates' 47th win was the opposition's inability to guard against their 3M Co. as Marte, Jordy Mercer and Andrew McCutchen combined to go 6-for-15 atop the lineup.
This marked the eighth time that threesome batted 1-2-3, and in those eight games they have batted .377 (40-for-106).
Before the second inning was over, Locke had more runs than in any of his previous 10 starts as the Bucs cooled off Saunders, who had been one of the American League's hottest starting pitchers.
"That was a different feeling," Locke said. "I could stay aggressive, keep the foot on the pedal. The breaking ball tightened up as I went along."
Saunders had allowed seven runs in the 34 2/3 innings of his previous five starts -- and only one fewer in the 1 2/3 innings of this start. Most of that damage came in the five-run second in which solo homers by Russell Martin and Marte bookended a three-run blow by Brandon Inge.
Of the three long balls, the hardest hit was Inge's -- a line drive deep into the lower deck for the veteran's first home run in 129 at-bats since Aug. 1, when he connected for the A's off Tampa Bay's Alex Cobb.
"That was as good for him personally as it was for the team," Hurdle said, and Inge did not disagree.
"Yeah, I don't like zeros in that stat," said Inge, who admitted having pressed a bit to break the ice. "Now maybe I can relax, and return to my normal swing."