World No.5 Angelique Kerber dug deep on Wednesday to book a quarter-final berth at the Brisbane International tennis tournament.

The 24-year-old fourth-seeded German looked down and out trailing 4-1 in the third set of her second-round clash with unheralded world No.124, 19-year-old qualifier Monica Puig of Puerto Rico.

Despite fighting back to force a third-set tiebreak, last year’s Wimbledon semi-finalist was again looking down the barrel when down 4-0 in the deciding tiebreak.

However, Kerber – the only player to down powerhouse world No.3 Serena Williams since the French Open in May – bounced back to save three match points before claiming a 3-6 6-4 7-6 (9-7) victory in almost two and a half hours.

She will next take on Russia’s Anastasia Pavlyuchenkova in the quarter-finals.