The Tunisian was down 7-6, 4-0 in the second round match with the two-time defending champion when she retired - she fell towards the end of the first set and required a lengthy medical break.
Second-seeded Petra Kvitova had no such problems, winning the last eight games to oust Viktoria Kuzmova 6-4 6-0 to book her spot in the last four.
"I feel close to my highest level", said Halep, the 2015 champion.
Pliskova, who missed nine chances to break her opponent, roared back in the second set to level the match without facing a single break point.
Halep reached the final in Doha last week and looks set to go similarly deep at this Premier 5 event after booking a last-eight spot in the United Arab Emirates.
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The challenger took a fall late in the opening set, potentially rolling her ankle while also hitting her shoulder.
The Romanian who is now without a coach, was more than pleased with her strong sprint finish to a match which lasted one hour, 20 minutes.
While Kvitova squandered her first match point by producing a 10th double fault, the Czech sealed a victory with a clinical point finished at the net. "I feel confident when I play her". "I tried to finish the points faster because I'm a little bit exhausted", Halep said. "I feel more relaxed in the final set, so I gained the match pretty well".
"For me, I just want to have the mentality of not thinking so much who is in the other side of the net", the 24-year-old said.
"And because a year ago I wasn't even anywhere close to this ranking and people didn't pay attention to me and that's something that I'm comfortable with". "I'm confident. I feel good on court even if I'm exhausted". Still just 21 year old, she is now the player with the target on her back, and this quietly-spoken young champion showed just what pressure she is under after an opening loss to the same woman she beat in Dubai last year, Kristina Mladenovic.
It was at this point that Osaka briefly broke down and had to hide her face as she wiped away tears.
"It means a lot, honestly", Mladenovic said after booking a match with a Spain's Carla Suarez Navarro in the last 16.