Joseph's three-run homer off Cubs starter Brett Anderson fueled a four-run first before the Phillies piled on for a 10-2 victory at Wrigley Field.
After Joseph sent his early blast into the left-field bleachers, the Phillies added three runs in the second, which gave starter Vince Velasquez all the cushion he would need. The Phillies gave themselves some insurance in the seventh inning on homers by Michael Saunders and Freddy Galvis.
But it was the previously slumping Joseph who got things started.
"To put up 10 runs is good for our offense, good for our team," Joseph said. "To be part of it is a good feeling."
Phillies manager Pete Mackanin called plating the additional runs "huge," citing the times this season when his team struck early but could not extend the lead. But behind Joseph -- who had only two hits in his last five games -- the Phillies pounded Cubs pitching for the 10 runs on 12 hits.
The timing couldn't have been better after a weekend sweep at the hands of the Dodgers.
"I still have adjustments to make," Joseph said. "It obviously felt good for me to do that, but it's more important for the team to get a win like that. [The Cubs are] the defending champions -- their team is pretty good top to bottom."
Mackanin was happy to see Joseph be the spark. Before the game, Mackanin said that he was willing to be patient with his slumping first baseman, but after Mackanin said he wanted to give Joseph about 100 at-bats to work through his struggles, Joseph needed just one to take a step in the right direction.
"If you want to play, you have to hit," Mackanin said. "And at some point, I think he's going to start hitting, and I'm going to give him every opportunity to do that, because I have a lot of confidence in him."
Joseph is coming off a season in which he batted .257 with 21 home runs and 47 RBIs in 107 games. That productivity, Mackanin said, is why the Phillies had so much hope as he made his first Opening Day lineup.
"I'm pulling for him," Mackanin said.
Joseph, for his part, knows there are still adjustments to make, but Monday's three-RBI performance was a step in the right direction.
Jeff Arnold is a contributor to MLB.com based in Chicago and covered the Phillies on Monday. This story was not subject to the approval of Major League Baseball or its clubs.