"Mr. Stanton is not available," Jennings said in an interview with SiriusXM Radio over the weekend. "He is going to be in right field at Marlins Park, and [we're] looking forward to having a big year with him. We're excited."
Stanton, 23, hit .249 with 24 home runs and 62 RBIs in his fourth season in 2013. He missed 36 games because of a hamstring injury a year after posting career highs in batting average at .290 and home runs with 37.
"We think it's going to be a lot of fun building around him and what he can mean to this ballclub and that city," Jennings said.
The Marlins finished last in the NL East this season for the third consecutive year, and it has been a decade since their most recent playoff appearance.
Their loss total has climbed each of the past four years, and despite the emergence of Stanton and several other young players, they finished with the worst record in the NL at 62-100.
Jennings was promoted to GM at the end of the season amid a franchise-wide shake-up in the executive ranks.
Information from The Associated Press was used in this report.