But they still feel sympathy for the face of the franchise, who both of them agree is working as diligently as possible to find his way out of the slump.
"It's tough, fans here take a little while to do that, they aren't quick to do that," Kennedy said of the booing. "But sometimes it's hard to watch your fellow teammate get booed. We know he's playing as hard as he can. He's come up in big situations a lot, it's not easy to produce every time. As a teammate, we feel for him."
On the season, Upton entered Thursday hitting .263 with seven homers and 34 RBIs. The batting average isn't too far off where he finished last season (.289), but the power and run production numbers are way down. In 2011, Upton hit 31 homers and drove in 88 runs.
The 24-year-old responded to the boos after Wednesday's game.
"To be honest, I don't care anything about what the fans think of me," Upton said. "My teammates, my coaches, they know I bust it every single day. I do everything to help this team.
"The fans can think whatever they want to think. They can call my lazy, I've heard that. They can call me washed up. Whatever they call me, at the end of the day, I'm thankful for every opportunity I get on the baseball field and I try my hardest every day."
Gibson said Thursday the connotation of Upton's words were different than how the actual context read.
"I think what he was saying was he knows he goes out and prepares for the game the same way either way," Gibson said. "Obviously he cares, if he didn't he wouldn't be working right now. He stays with it and plays the game very well."
Again, Gibson acknowledged that fans booing players when they are not performing well is part of the game, but he still hopes that it quiets down for Upton's good.
"I'll say this about the fans: Let's stop and think about it. Do we want him to do good? Would booing help motivate someone?" Gibson said. "We all understand why they do it, but [Upton] cares about everything he does. I've been booed several times. It's because they have high expectations."