The 2021 US Open champion, ranked 77th, faces Poland's Magda Linette next at the prestigious tournament.

"I didn't feel too good this morning," she told BBC Radio 5 Sports Extra.

"I'm just so happy with the way I fought and dealt with the circumstances.

"I just woke up feeling not great to be honest. I felt quite ill so I'm just happy to have played the match and then to win it despite how I felt today.

"Today before the match, I did not warm up. Two minutes before I was called I was sleeping in the treatment room so I'm just proud to have got out there and then won."

In the men's draw, Andy Murray defeated Tomas Etcheverry 6-7 (5-7) 6-1 6-4 to reach the second round while fellow Briton Jack Draper needed just 55 minutes to win his opener, beating Switzerland's Leandro Riedi 6-1 6-1 to set up a meeting with compatriot Dan Evans.

Indian Wells is one of the biggest events outside of the four Grand Slam tournaments.

Since sensationally winning the US Open as a virtually unknown teenage qualifier, Raducanu has been unable to build on that success as her progress continues to be stalled by fitness problems.

Various injuries over the course of 2022 wrecked her chances of finding momentum in her first full year on the WTA Tour and the wrist problem that ended her season returned to threaten her participation in Indian Wells.

With tonsillitis also forcing her out of a tournament in Austin last week, the British number one summed up her fortunes by telling BBC Sport: "When it rains, it pours."

But an efficient victory over 62nd-ranked Kovinic - in Raducanu's first match since losing to Coco Gauff at the Australian Open - should help lift any lingering gloom.

Raducanu trailed 2-0 in each of the two sets, but grew in confidence as 28-year-old Kovinic produced a stream of errors.

Kovinic played some loose shots and struggled with her first-serve percentage in both sets, with Raducanu staying patient and playing smart to grind out a solid win.