Valter, 22, broke free during the final few kilometers and the peloton was unable to catch him.
In the second minute after kick-off, Rondon scored the opener with his left foot. Rondon extended the lead for Dalian in the 29th minute, as he assisted Marek Hamsik to slot home.
Flamengo netted twice in quick succession after the restart: first with a stunning first-time effort from playmaker Everton Ribeiro and then with a cool Arrascaeta finish after a counterattack.
There were also second round wins for fourth seed Stefanos Tsitsipas of Greece, fifth seed Alexander Zverev of Germany and seventh seed David Goffin of Belgium.
"It's a great motivation for me to want to do well this tournament, but for the most part I feel like I've been in quarantine and practising for so long, so I prefer to play matches," Osaka said.
Earlier, sixth seed Petra Kvitova of the Czech Republic edged past Ukraine's Kateryna Kozlova 7-6 (3), 6-2, and eighth seed Petra Martic of Croatia beat fellow Ukrainian Kateryna Bondarenko 6-3, 6-4 to also advance into third round. Enditem
"Prize money and allowances have been equalled for men's and women's football, which means female players will earn the same as the men," Brazilian Football Confederation (CBF) president Rogerio Caboclo said in a virtual news conference.
"COVID-19 brought us lot of challenges, which were highlighted in the copyright negotiations. We are regretful to announce the termination with Premier League despite rounds of negotiations," read a statement.
"There have been other instances where we have tried to go but the club won't allow it, or they've done something. I want to play football, I am still motivated to play football, so I guess it's on the club. They are in control of everything. I have a contract, all I can do is carry on what I am doing and hopefully something comes up," said Bale. Enditem
"Our development will not be redirected. It is just a strategic adjustment based on reality. We will continue to hand the best services to our fans and partners," it added. Enditem
He doubled Flamengo's lead with a low shot that rebounded in off the post before Rodriguinho pegged a goal back for the hosts.