The British star impressed during a run to the quarter-finals at the Miami Open and Navratilova has urged her to build on the strong performance by working with a coach for an extended period.

The 18-time Grand Slam singles champion told Sky Sports Tennis: "If she stays healthy and plays this well, then she'll be seeded at Roland Garros. I think she'll move up the ranking well enough into the top 30. The biggest question mark is her health.

"Hopefully she can sort out her coaching situation because she's been in a state of flux, but I think she needs to commit to somebody and stay with them for a little bit, see how that works.

"If she played like she did against (Jessica) Pegula, then the sky's the limit."

Navratilova was impressed with the former US Open champion's battling qualities in her loss to Pegula as she was able to make the match last the distance despite feeling unwell.

She said: "It was amazing. The way she looked at the end of that second set, you think this match is over and somehow she won the set, she won the tie-break, and still competed in the third but she was not feeling well.

"I think the stress contributed to that because the weather was fine, it was cool, they finished after 11pm so the weather was [not a factor]. The humidity takes it out of you a lot, but still - this was something more for Emma and it's just amazing that she finished the match."