Upton, who has yet to play a Major League game this season, played in a doubleheader Wednesday for Double-A Montgomery with no reported setbacks.
"He should be, no reason to think he shouldn't be," Maddon said, when asked if Upton would be ready for Friday. "Every reason is that he would be back. There would have to be something unforeseen happening between now and then."
In seven rehab games between Class A Charlotte and Double-A Montgomery, Upton hit .143 (3-for-21) with two runs scored, two RBIs and a pair of stolen bases.
"I've heard good things," Maddon said, about Upton's rehab assignment. "A lot of good contact, he's moving well, good at-bats, legs are good. His typical game is coming back in order."
Upton provides the Rays with another right-handed power bat to pencil in the middle of the order and his combination of power and speed is something his skipper is looking forward to getting back.
"B.J. definitely makes us a better team," Maddon said. "We saw the way he finished the end of last season. It may take a little time to get him going, based on a sporadic Spring Training and then going on the rehab assignment, but it's good to get him back. Makes everything better. Makes our defense better, adds more speed to the bases and a power bat. Definite improvement for us."
The 27-year-old stole 36 bases last season after swiping 40-plus the previous three years, and hit 23 homers in 2011, one off his career high set in 2007. He finished the season strong, hitting .333 in September with five homers and 20 RBIs, while swiping nine bases.
His return will shift Desmond Jennings, who has been playing in center, over to left field. Maddon is excited about how much stronger Upton's range makes a Tampa team that is already strong defensively.
"It's so nice," said Maddon, when asked how beneficial his defense is to his pitchers. "When you stand in the dugout every night and watch us on the field, we've gotten really spoiled. When the ball is hit, you know you have a pretty good shot of catching it.
"We cover well in the outfield, our infield covers the same kind of game on defense. We are fun to watch on defense."
Upton was placed on the disabled list on April 4 with a sore lower back retroactive to March 26. He has been out since March 14 after a collision with Jennings.