Australian Open champion -- and the sport's new superstar -- Osaka withdrew last week due to a back injury, leaving a big hole to fill for tournament organisers, which they have done with a strong field including three former world number ones.
All three were formerly at the top of the women's rankings, Halep only being ousted by Osaka last month after Melbourne.
Halep, now ranked three in the world, and Kerber, sixth, are both Grand Slam winners. Pliskova, the world number five, is a former US Open finalist.
"It's a tough draw [in Doha]," Kerber told reporters on Sunday. "But this is a challenge, and I'm always looking forward to coming here." All three top seeds have a good record in Qatar.
Halep and Kerber met in the 2014 final, with the Romanian winning, and Pliskova won the title two years ago.
The Dane was the runner-up to Pliskova in 2017.
But the 24-year-old now feels she is ready to return to the court earlier than anticipated.
"This tournament, you know, here is always tough," she said.
"Everyone wants to play, everyone wants to play well. That's why it makes it not easy at all." The top four seeds are expected to be in action from Tuesday.
Halep and Pliskova could meet in the final in Doha, just days after the pair were set to meet against each other this weekend in the Fed Cup.
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