World number one Halep looked to be in trouble against the supposedly modest talents of Dodin, but she showed her class to progress in Miami.

It was a mixed day for the other seeds, but Pliskova – ranked sixth – and two-time grand slam champion Kerber – ranked 10th – both made it through, with Caroline Garcia a notable departure.

Former world number one Victoria Azarenka, meanwhile, benefited from Madison Keys' retirement.

Top seed Halep reflected on a "crazy game" after she edged past Dodin, coming from a set down to beat a player who had only qualified as a lucky loser.

Dodin's power repeatedly caused the Romanian problems as she looked to be suffering initially with her neck and then with her ankle, but a two-hour marathon proved too much for the world number 98.

"This year I have had many tough matches," Halep said afterwards. "I'm used to it."

Having avoided her earliest exit since 2011, she will look for a more comfortable progression next time out against Agnieszka Radwanska.

Pliskova was also tested as she edged out Ekaterina Makarova 7-5 7-5 to remain on course for a quarter-final meeting with Halep.

German star Kerber is a potential last-four opponent for the pair, meanwhile, after a routine 6-2 6-2 defeat of Johanna Larsson.

Not every seeded player made it through, though, with Garcia comprehensively beaten 6-3 6-1 by Alison Riske, while fellow qualifier Monica Niculescu saw off Magdalena Rybarikova.

US Open champion Sloane Stephens, however, was too good for Ajla Tomljanovic 6-1 6-1.

A hamstring problem forced Keys to retire when the 14th-seeded American was trailing Azarenka 7-6 (7-5) 2-0 on Thursday.

US Open finalist Keys called for the trainer between sets but she was unable to continue after falling behind a break against the Belarusian star.

Azarenka will face 20th seed Anastasija Sevastova in the third round.