Cerundolo knocks out Ruud in Miami, Djokovic eases into quarters
Cerundolo, who enjoys plenty of support from South Florida's large Argentine community, has now reached the last eight in three of his past four appearances at Miami.
Cerundolo failed to make the most of three break points in the opening game but eventually broke through at 3-3, converting his fourth break point of that game.
The 23rd seed, who lost to Carlos Alcaraz in the quarter-finals at Indian Wells, was dominant in the second set, but his victory was postponed by a three-hour, 30-minute rain delay that arrived when he was 5-1 up.
"I'm super happy. It’s always difficult when you’re playing a really good match, controlling the game, and you have to stop for rain," said Cerundolo.
"It's not easy, but I was chill and came back to the match confident and played a really good service game. I'm super happy to get back-to-back Masters 1000 quarter-finals in the US, on hard courts. It's a great achievement," he said.
Next up for Cerundolo is 14th seed Grigor Dimitrov, who defeated American Brandon Nakashima 6-4, 7-5.
Novak Djokovic cruised his way into the quarter-finals with a 6-2, 6-2 win over Italian Lorenzo Musetti in one hour 22 minutes.
Musetti, the 15th seed from Tuscany, got off to a flying start taking a 2-0 lead in the first set but then proceeded to lose the next nine games as the Serb, looking confident and sharp, ran away with the game.
Djokovic has won the Miami Open on six occasions but has not featured in the quarters since his last victory here in 2016.
The 37-year-old is now just three wins away from winning his 100th tour-level title
There was some cheer for the home crowd with Sebastian Korda beating French veteran Gael Monfils 6-4, 2-6, 6-4 in another rain-affected match.
Korda visibly struggled with his wrist, however, and said after the match that he had been in discomfort with an injury that has caused him trouble in the past.
"It’s pretty painful right now, we’ll see how it goes tomorrow. Will do a lot of work with my physio now, we’ll see how it is tomorrow.
"I haven’t played a lot of tournaments this year. Hopefully I can play some good tennis and see where it takes me," he said.
Korda later pulled out of his doubles match with partner Jordan Thompson.
The rain delay meant that top-seed Alexander Zverev's fourth-round match against France's Arthur Fils has been postponed until Wednesday.
German Zverev's match, which was scheduled to be the final contest of the day on stadium court, is the day's only singles match that was pushed to Wednesday.