There may be the perception that the Rays' center fielder is doing better because he's finally putting his poor start behind him, or that moving down in the order has relaxed him or that he's finally starting to come into his own after missing all of Spring Training and the early part of the season coming off shoulder surgery.
But manager Joe Maddon said it has everything to do with the timing of his left foot.
Before a hitter's hands can get going to begin a swing, the front foot needs to come down. Earlier this year, Upton was late with that, and sometimes even the most average of fastballs was beating him.
Now, that has changed.
"He'd been having a hard time getting that foot down in time, because his foot does a lot," Maddon said. "If you really watch him closely, his front foot does a lot of movement before he actually swings -- kind of unusual, actually. He's got so much front-foot movement that if that's not there on time, even a mediocre fastball can beat him. But if that foot's there on time, the best fastball can't beat him."
Upton has been spending more time in the cages lately, working with hitting coach Steve Henderson to try to get back to the explosive player he's been the past couple of years.
Henderson said the 24-year-old speedster, whose birthday is Friday, also is starting to calm down.
"He's not trying to make things happen; he's just trying to relax," Henderson said. "It looks like he's having more fun."
It's easy to have fun when you've had the games Upton has had the last couple of nights, when he's gone a combined 4-for-7 with two home runs, three RBIs and two runs scored.
"I'm feeling a lot better up there, a lot more confident," Upton said after Wednesday night's 3-1 win.
His numbers still weren't pretty going into the series finale against the Orioles at Tropicana Field on Thursday, with a.241 season average, but Upton simply is an exciting player to watch when he's going full steam, and the last couple of games may be an indication that's about to happen.
"B.J. is one of the most talented players I've ever seen in my life, and it's always fun to see him just click," first baseman Carlos Pena said. "He's been through so many injuries and stuff like that, so I have a lot of respect for him, because he's a very tough kid.
"He's one of the most incredible talents in the game, and it's really stunning to see. I'm just glad I have a good seat to watch it."
Alden Gonzalez is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.