CHICAGO -- As Matt Duffy entered the dugout following his first career grand slam against the Pirates on Sunday afternoon, Frank Schwindel noticed that Duffy couldn’t help but celebrate a little more than usual.

“That was so fun to watch,” Schwindel said about Duffy’s third-inning blast. “He came into the dugout and said something like, ‘I’m not even gonna hide this smile and pretend I've done it before. That was awesome.’”

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Duffy is less than two years older than Schwindel, but he made his Major League debut in 2014 and has played in almost 500 more games. But maybe seeing a veteran like Duffy celebrate as if it were his first home run in the Majors helped Schwindel understand that, sometimes, it’s OK to act like you haven’t been there before.

Schwindel later stepped to the plate in the bottom of the seventh with the bases loaded and two outs and the Cubs down a run. After working a 2-2 count, Schwindel unloaded to left-center field on a curveball well below the strike zone and dropped it into the basket hanging over the Wrigley Field ivy.

That grand slam was the difference as the Cubs won, 11-8, and finished off their first four-game sweep of Pittsburgh since taking four in a row at PNC Park from Aug. 1-4, 2011. And even though Schwindel had been there before -- frequently, as it was his sixth home run in his last seven games -- he still celebrated in the dugout in a way that would’ve made third-inning Duffy proud.

“Frank's just got this thing on repeat right now,” Cubs acting manager Andy Green said. “Going to ride it as long as we can and not ask questions about it. [We’ll] leave that to you guys and just let him keep doing his thing.”

Duffy hadn’t homered since mid-May, but his grand slam was his second big fly of the game. He got Chicago on the board in the second inning with his first career home run at Wrigley, and Jason Heyward’s homer to right in the next at-bat made it a 2-1 ballgame. Then, after Pittsburgh center fielder Bryan Reynolds gave the Pirates the lead with a grand slam off Zach Davies in the third, Duffy matched him in the bottom of the frame with his first career grand slam, sending the crowd into a frenzy.

“Duff hasn't necessarily driven the ball out of the ballpark very often, but he has a ton of big at-bats for us and just gets hits for us in big situations,” Green said. “To see him do that today was great.”

Added Duffy: “It feels good. I was just going around all day saying, 'Somebody pinch me! Somebody pinch me!’”

When Green was asked Saturday morning whether he’d figured out who filled in for him as manager when he was ejected from Friday’s game, he still found a way to end his answer on a completely separate topic.

“As long as Frank Schwindel keeps hitting home runs, we're gonna be OK,” Green said.

So it seemed almost poetic that when Pittsburgh was up 8-7 in the bottom of the seventh and the Cubs loaded the bases with two outs, none other than Schwindel stepped to the plate. The Pirates made a pitching change to bring in right-hander Nick Mears, but Schwindel needed just five pitches to take him deep for his first career grand slam.

Overall, Duffy and Schwindel combined for three of the Cubs’ four home runs, nine of their 11 RBIs and six of their 13 hits, and Chicago now enters a new week riding a six-game win streak.

“It's fun,” Green said. “They're great guys, they work incredibly hard. They both are really good baseball players, and you're seeing it on the field.”

“Deep down, we want to compete, we want to be good. We're not just going to coast the rest of the year,” Schwindel said. “It's a lot of fun when everybody’s on the same page and putting the work in and seeing some results.”