The two teams play Friday at Ladd-Peebles Stadium in a game that's important to both programs.
A win would send Navy (5-5) to the Poinsettia Bowl for its 11th postseason trip in 12 years. The Midshipmen's only other chance to become bowl eligible would be Dec. 13 against Army, just 10 days before the bowl game.
''We may get left out if we have to wait for the Army game,'' coach Ken Niumatalolo said. ''We don't know. There's so many different variables. We've got to find a way to win this week. They're trying to win more games, too, to up their stock to make sure that they don't get left out. This is a big game for both of us. For both of our programs, this is a must-win.''
South Alabama (6-5), which plays in the Sun Belt Conference, is already eligible for a bowl. A win over the Midshipmen would help the Jaguars' case for receiving the first bid for the still-young FBS program. South Alabama was 6-6 last season but didn't get invited to a bowl.
Navy won the only previous meeting 42-14 last season. This game concludes the home-and-home series.
''Getting a program like Navy to come here is a big deal,'' said Jaguars coach Joey Jones, whose program was started in 2009. ''We want to play teams like that.
''They're a nationally-known team that took Notre Dame down to the wire and beat Georgia Southern last week. They're a very good football team and everyone knows it. If you can somehow get in there and beat them, it becomes something you put on the wall forever in a place like ours. So it's a great opportunity for us.''
Here are some things to watch in the game:
KEENAN CAN: Navy quarterback Keenan Reynolds is coming off a career game. He ran for 277 yards and six touchdowns, a Navy-Marine Corps Memorial Stadium record. His 58 career rushing touchdowns trails only Nebraska's Eric Crouch and Nevada's Colin Kaepernick among quarterbacks.
FACING TRIPLE OPTION: South Alabama has faced one triple option offense already. The Jaguars allowed 335 rushing yards in a 28-6 loss to Georgia Southern in September. Jones' counsel to his defenders: ''let's not get overwhelmed by what they're doing. Are they good at it? Yeah,'' he said. ''Is it a different offense? Yeah, but what we're asking you (defense) to do is the same thing we ask you to do all the time which is play good technique football.'' Navy's 354.8 rushing yards per game leads the nation. South Alabama ranks 76th in run defense, giving up an average of 172.7 yards.
TURNOVERS: Both teams have had trouble coughing up the ball. Navy ranks 83rd in turnover margin while South Alabama is 100th and committed five turnovers in last weekend's loss at South Carolina.
NAVY'S MOMENTUM: The Midshipmen are trying to maintain momentum heading into the game with Army. They've won three of their last four games, with the only loss coming in a competitive game with then-No. 6 Notre Dame.
SOUTH'S SENIORS: Some of South Alabama's 32 seniors have been there since the second year of the program and have been part of the Jaguars' move into the Sun Belt. This could be their finale.