Jennings is starting in left field and batting second against Toronto. Navarro is catching and batting eighth, one spot behind former Colorado Rockies All-Star Brad Hawpe, who was the designated hitter in his Tampa Bay debut.
Among other moves, reliever Grant Balfour was activated from the 15-day disabled list. Right-hander Jeremy Hellickson was recalled from Class-A Charlotte and will pitch out of the bullpen.
The Rays also purchased the contract of outfielder Rocco Baldelli from Durham, recalled catcher Jose Lobaton before placing him on the 15-day disabled list with a right foot injury, and sent right-handed reliever Dale Thayer outright to the Triple-A affiliate.
Hawpe signed a minor league contract last week and played two games at Charlotte. The Rays purchased his contract on Tuesday.