Serena Williams returns with exhibition loss to Jelena Ostapenko

— -- Serena Williams returned to the court for her first competitive match in almost a year with an exhibition loss to Jelena Ostapenko at the Mubadala World Tennis Championship in Abu Dhabi on Saturday.

Williams quickly dropped the first set 6-2 against Ostapenko, the French Open champion who is ranked No. 7 in the world rankings. She then rebounded to win the second set 6-3 but quickly fell behind 5-0 while losing the match tiebreaker 10-5.

The 36-year-old Williams had not played since winning her 23rd Grand Slam title at last year's Australian Open while approximately eight weeks pregnant.

"I'm excited. It's good to be back on the court," Williams said after the match. "This was such a good time for me. ... First matches back are always super-incredibly hard, especially after having a baby. It was great. I was glad I could do it here."

During her time off the court, Williams gave birth to Alexis Olympia Ohanian Jr. and married her daughter's father, Reddit co-founder Alexis Ohanian, in November.

Williams said after the 67-minute match that she is still undecided on her title defense of the Australian Open, which starts Jan. 15, but delivered a warning to rivals.

"I don't know if I am totally ready to come back on the tour yet. I know that when I come back I definitely want to be competing for championships," Williams said. "I am definitely looking forward to getting back out there.

"I am taking it one day at a time. I am going to assess everything with my team before deciding."

Australian Open tournament director Craig Tiley said earlier this month that Williams was "very likely" to defend her title in the first Grand Slam of 2018.

The Associated Press contributed to this report.