Roger Federer has retained his top ranking and equalled his career-best start to a season with a straight-sets quarter-final win over Hyeon Chung in Indian Wells.

Federer's 7-5 6-1 victory improved his record this year to 16-0, matching his 2006 season start, and propelled him into the semi-finals in his title defence in the Californian desert.

With Rod Laver and Pete Sampras looking on, the great Swiss fired 12 aces and was broken just once in extending his bid for a record sixth Indian Wells title.

Federer and Chung last played in the Australian Open semi-finals, when the South Korean was forced to retire trailing 6-1 5-2 because of blisters on his left foot.

Federer went on to win the title and, at 36, is world No.1 again.

But he needed to make the final four this week to avoid relinquishing top spot to Rafael Nadal.

Federer saved a handful of break points in the first game of the second set and then broke Chung twice, including on a double fault to take a 5-1 lead.

Serving for the match, Federer's errant backhand spoiled his first match point. His forehand volley went wide, giving Chung a break chance. But Chung's forehand error got Federer to deuce and he closed out his second match point with an ace that Chung unsuccessfully challenged the call on.

Next up for Federer is Croatian Borna Coric, who upset No.7 seed Kevin Anderson 2-6 6-4 7-6 (7-3) for his first win in four tries against the South African.

The 21-year-old Coric will be play in his first Masters 1000 semi-final against the record-setting top seed.

The unseeded youngster initially looked outgunned by the 2017 US Open finalist.

But after weathering an onslaught of huge serves from Anderson in the first set, a scrappy Coric was able to force longer rallies in the second and third.

The match appeared all but over when Coric double-faulted to hand Anderson a break for the 4-2 lead in the decisive third set but the world No.49 broke straight back and went on to force a tiebreaker.

Anderson played a mistake-riddled breaker and Coric pumped his fist in triumph after his opponent sent a forehand long to hand him the biggest win of his career.