Britain's Jamie Murray and his partner Bruno Soares cruised into the last four of the ATP Finals by beating Marcelo Melo and Lukasz Kubot.
Melo and Kubot are ranked one and two respectively in the doubles rankings but they were outclassed at London's O2 Arena as Murray and the excellent Soares won 6-2 6-4.
"We played great again," Murray said. "We knew we'd have to play a really good match to bet Marcelo and Lukasz.
"Obviously playing the way we did on Wednesday gave us a lot of confidence going into this match. We played great again from start to finish really."
This was an all-or-nothing tie for Murray and Brazilian Soares, who knew success would mean progressing as group winners while defeat would see them eliminated.
Their triumph therefore earns them top spot but arguably a tougher semi-final draw, given they now face defending champions Henri Kontinen and Murray's former partner John Peers on Saturday.
Kontinen lifted the Wimbledon mixed doubles trophy alongside Britain's Heather Watson last year.
"It's going to be tough again, obviously," Murray said. "We lost to them twice this year, both in tiebreaks, both close matches.
"They're a power team, with big serves, they like having cracks at returns. It's not like you get a lot of rhythm playing against them."
Murray had also called for treatment during his last match on Wednesday for spasms in his back and the Scot took the day off practice on Thursday to recover.
"It's better, I wasn't really aware of it so much when I was playing," Murray said. "It's not always that comfortable but it's not really affecting me playing."
Melo and Kubot go through as runners-up in the group and will meet Ryan Harrison and Michael Venus in the other semi-final.
Soares and Melo know each other well from playing regularly together for Brazil in the Davis Cup while Murray has also partnered Melo in the past.
Kubot and Melo had already qualified regardless of this result and there was a noticeable difference in the teams' intensities, particularly in the opening set.
Two stinging Soares returns earned him and Murray a break on Melo's serve and then Kubot was also broken when his own lob dropped long on a deciding deuce.
Down 5-0, Melo lashed an overhead long and was fortunate not to catch a ball girl when he irritably whacked a ball in her direction.
Murray and Soares squandered five set points - four on Soares' serve - but finally converted a sixth when a quick exchange at the net ended with Soares sweeping a backhand down the line.
An early break of serve put Murray and Soares in command in the second but Murray gifted a break back with a double fault and then had to save three more break points at 3-3.
The threat of a Kubot-Melo comeback was fleeting, however, as Melo double faulted at 5-4 before a Kubot volley landed long to confirm their opponents' victory.