
The Serb, ranked third in the world, was unable to continue just 14 points into her women's singles just hours earlier at the eight-nation, mixed teams event, retiring after one game to France's Tatiana Golovin.
Jankovic went for a scan at hospital, which showed no tear of the muscle. With that somewhat reassuring news to hand, she decided to give the deciding mixed doubles a go.
Serbia and France stand level 1-1 in their tie after Novak Djokovic beat veteran Frenchman Arnaud Clement, France, 6-3, 6-3 to pull the scoreline back.
Jankovic won the Wimbledon mixed with Jamie Murray and has the most experience on the court in the esoteric team game.
"I'll have to reply on her even if she's injured," said Djokovic, who praised his own serve as the key to winning over Clement, the 2001 Australian Open finalist.
"The French play a great mixed. It's always good experience to play with female," said the 20-year-old jokester of the game. "You can kiss at the end and kiss at the start of the match."
Djokovic double-faulted on his first match point against Clement, finally closing out victory on his third winning opportunity.
The Serb posted 24 unforced errors, seven aces and broke on four of eight occasions.
Jankovic suffered her injury midway through the opening game of the match at the Burswood dome. She won the game, then took treatment on and off court.
She came back out and played two points before giving up.
"I had just finished warmup and saw her in locker, barely walking," said a surprised Djokovic. "If she can play the mixed, it's a good thing - hopefully we can win."