Butler BlueSox first baseman David Marcus extended his Prospect League lead in home runs by hitting a ball 388 feet to the warning track.

Jamestown Jammers center fielder Dominique Jackson accidentally did Marcus a favor, carrying the ball an extra three feet over the wall.

Jackson caught the towering fly ball, took three steps and jumped into the fence.

The collision caused the ball to pop out of Jackson’s glove and tumble over the wall, plating the first run in the BlueSox’ 4-1 East Division win Wednesday night at Kelly Automotive Park.

No one was more surprised than Marcus, who was headed back toward the dugout.

“I was like that was just a fly out, I put a good piece on the ball, but bad luck,” Marcus said. “Then (Butler first base coach Cody Herald) told me (Jackson) put it over the fence and the umpires gave the home run signal. It was one of the more awkward trots I had playing baseball.”

Marcus shouldn’t be too far out of sync with his home-run trot.

He’s practiced it plenty this season. Marcus — who also smacked a solo home run that needed no help clearing the right-centerfield fence in the fourth inning — leads the league with seven home runs.

“He has great plate coverage,” Jammers manager Anthony Barone said. “The only way you can beat him is to throw hard and in. He has good plate coverage and good discipline in the zone.”

Marcus finished second in the league’s home run derby and also has a league-best .373 batting average.

At California (Pa.) University in the spring, Marcus led the Vulcans with 15 home runs.

“It’s not like he doesn’t have power, it’s all of a sudden it’s coming on,” Butler manager Jason Radwan said. “He’s squaring up the baseball, looking for his pitch to hit and he’s driving them.”

Marcus’s two home runs doomed the struggling Jammers, who have tumbled to 21-19 overall and 2-8 in the second half during their six-game losing streak.

“It’s been like this for the last couple weeks where we don’t hit,” Barone said. “Our pitchers have been doing a great job, we score one, two runs a game and that’s what we’re doing.”

Butler (20-18, 7-4) added two insurance runs in the fourth inning on a triple by Matt Hansen.

Vinny Mallaro drove in the Jammers’ lone run with a one-out single in the sixth inning.

The BlueSox duo of Tyler Slepski and Zach Spangler kept Jamestown’s offense down.

Slepski, a Butler High School graduate, allowed three hits, one run and struck out two in eight innings.

Spangler struck out two in the ninth, setting Butler’s record by recording his 14th save.

Adam Dian had the previous record, which he set in 2012.

“He’s been lights out all year,” Radwan said. “First day of mini-camp they threw pens and he really didn’t close at Kent State. He was a setup guy and right specialist, talked to him about closing and he really wanted to do it. He thrives in that role.”

Spangler recorded one save in his freshman season at Kent State.

“I knew what the role was like and got the taste of it,” Spangler said. “It’s different, but I like the challenge and love the closing role. It’s a lot of fun.”

Marcus doesn’t expect much more generosity from opponents this season.

But he’s hoping the BlueSox continue to come up with timely hits, however they may come.

“Key hits,” Marcus said. “Clutch-hitting at first wasn’t there for us. A lot of two-out RBIs helping us out, as a whole getting on base and putting pressure on the defense.”

Jamestown 000 001 000 — 1 3 2

Butler 010 120 00x — 4 4 0

W: Tyler Slepski 8IP (2K, 0BB). L: Josh Shailer 6IP (K, BB). S: Zach Spangler 1IP (2K, 0BB).

Jamestown (21-19, 2-8): Vinny Mallaro 1B RBI, Nick Vehlewald 1B 2B.

Butler (20-18, 7-4): David Marcus 2-HR 2-RBI, Matt Hansen 1B 3B 2 RBI, Dan Hrbek 1B.

Today: Quincy Gems at Butler, doubleheader