Maybin, who missed all but 14 games in 2013 due to injuries, robbed the Dodgers' Juan Uribe of extra bases in the fourth inning of a game in Glendale, racing from center to right for a catch. But between pitches to the next batter, Maybin dropped his glove and was in obvious pain.
"When he landed, it jarred the shoulder and did damage to the biceps tendon," said Padres manager Bud Black.
Maybin won't return to the Padres' complex in Peoria until Wednesday at the earliest, as he was headed to North Carolina on Monday afternoon because of a death in the family.
Black was asked if Maybin should have been more cautious, especially in an exhibition game.
"The thing about a play like that ... you can't play at a lesser level, you've got to play a Spring Training game like a regular-season game," Black said. "You have seen players [in spring] play hard. Cam is a guy who plays the game like it's meant to be played."
The injury came a day after Maybin hit his first home run of the spring.
Last season, Maybin spent time on the disabled list with first an impingement to his right wrist, which later required season-ending surgery. Maybin also missed time after he tore the posterior cruciate ligament in his left knee.
Maybin hit .264 with nine home runs and 40 steals in his first season with the Padres in 2011. He then hit .243 the following season.
"It's a tough story," Black said. "He did a diligent job this past offseason of rehabbing both the knee and wrist and was feeling great coming into this camp. He had the home run up in Surprise. He was running well and put on some muscle and was in a good spot. It's a tough one personally for Cam and us. We all feel for him."
Will Venable is the likely candidate to see time in center field, as he did a year ago when he appeared in 80 games there. Venable actually rated very well in center field, posting a 4.8 UZR (ultimate zone rating) last season compared with a minus-7.8 UZR in right field.
This means Chris Denorfia and Seth Smith will likely share right-field duties with Carlos Quentin handling left field and Denorfia and Smith also seeing time there. Utility man Alexi Amarista could also see time in center field again.
"We like our depth, but losing Cam for any period of time would hurt," said Padres general manager Josh Byrnes. "We do have some depth and guys we can move around."
Maybin signed a five-year, $25 million contract extension in the spring of 2012. He'll make $5 million this season, $7 million in 2015 and $8 million in 2016. There's a $9 million club option for 2017 that includes a $1 million buyout.