LONDON (AFP) - Angelique Kerber was on the brink of losing the world number one ranking on Saturday (July 8) before the German scraped into the Wimbledon last 16 with a tense 4-6, 7-6 (7/2), 6-4 victory over Shelby Rogers.

In order to retain top spot in the WTA rankings, Kerber has to return to the Wimbledon final 12 months after losing the title match against Serena Williams.

The 29-year-old was on the verge of crashing out in the third round after losing the first set and falling a break down in the second against American world number 70 Rogers.

But Kerber, who won the Australian and US Opens last year, gamely battled back to level the match in a second set tie-break before edging through in the decider.

Kerber faces Spanish 14th seed Garbine Muguruza, another former Wimbledon runner-up, for a place in the quarter-finals.

If Kerber, who regained the top ranking from Serena in March, fails to make the final she will surrender pole position to Romania's Simona Halep or Czech Karolina Pliskova.