Rafael Nadal's Spain eased into the quarter-finals of the Davis Cup on home soil while Novak Djokovic helped Serbia make a fast start to their campaign.
It was nearly 2am on Wednesday morning when Spain completed victory over Russia but they made much shorter work of a severely-weakened Croatia in the evening to send the defending champions tumbling out.
Croatia's chances took a major hit with the withdrawal pre-event of Marin Cilic, and they were also without Borna Coric on Wednesday.
Doubles specialist Nikola Mektic had to play singles against Roberto Bautista Agut, losing 6-1 6-3, before home hero Nadal saw off Borna Gojo 6-4 6-3.
While the main arena was again rocking for Spain's tie, it was a different story in the morning for Serbia's clash with Japan, but Djokovic shrugged off the lack of atmosphere in a speedy 6-1 6-2 victory over Yoshihito Nishioka.
That secured the most comfortable of victories after Filip Krajinovic had earlier beaten Yuichi Sugita 6-2 6-4, with the doubles team of Janko Tipsarevic and Viktor Troicki completing a 3-0 whitewash.
The radical changes to the event have been the hot topic of conversation so far this week and Djokovic voiced his hopes that the Davis Cup and ATP Cup will eventually merge.
The ATP Cup will have its inaugural edition only six weeks after the end of this event to kick off the new season.
Djokovic, the president of the ATP Player Council, has been a big advocate for Davis Cup reform, and he said: "When you make a change, it's always going to be a risk.
"I'm sure that organisers of this event are doing their best to make this a successful week. It's a lot of responsibility and pressure on them because this is the most traditional, historic team event in our sport, over 100 years. So there's a tremendous burden of history on them to make it right."
Djokovic may well have piqued the interest of Roger Federer on his exhibition tour of South America with his suggestion that the perfect time for a flagship team event would be at the end of September, the position currently occupied by Federer's Laver Cup.
"Looking long-term, I personally don't think that the two events can co-exist six weeks apart. It's just a little bit too congested," Djokovic added.
"The most ideal, I think, time of the year is after the US Open, probably end of September. That would be the best time to have this super cup hopefully in the future."
Djokovic, meanwhile, criticised the situation that emerged on Tuesday night when Canada were allowed to forfeit their doubles rubber against the USA having already won both singles matches.
That put the Canadians through to the quarter-finals but, with the two best-placed runners-up across the six groups progressing to the last eight, the 6-0 6-0 scoreline awarded to the US could help them in comparison to other teams.
"I personally don't like that. That shouldn't be allowed," Djokovic said.
"That 6-0 6-0 might make a big difference in the calculations for the second-best teams. So I don't think that's fair. I think everyone should be obliged to come out and play."
The International Tennis Federation said that Canada were permitted not to play the rubber because three of their four players were passed unfit.
Teams are allowed to have five players but Canada chose not to replace Milos Raonic when he pulled out through injury.
Andy Murray was also critical, saying: "I don't think that's good."
The scheduling will also need to be addressed by organisers after the start of the evening session on courts two and three was delayed by nearly two hours because of long afternoon ties, making another very late finish a near certainty.
Germany sprang a surprise by beating Argentina 3-0 to give themselves a great chance of reaching the quarter-finals.
Philipp Kohlschreiber recovered from a set down to defeat Guido Pella 1-6 6-3 6-4 while Jan-Lennard Struff was a 6-3 7-6 (10-8) winner over top-20 player Diego Schwartzman.
Doubles pair Kevin Krawietz and Andreas Mies then won the longest tie-break in Davis Cup history, taking the deciding set 20-18 against Maximo Gonzalez and Leonardo Mayer.
Check our news, reports and reaction from all major tennis events by following us on skysports.com/tennis, our app for mobile devices or our Twitter account @skysportstennis.