Briton Joe Salisbury and Rajeev Ram have reached the ATP Finals last four for the first time, beating Germans Kevin Krawietz and Andreas Mies.
The Australian Open champions won 7-6 (7-5) 6-7 (4-7) 10-4 in London.
Krawietz and Mies had two set points at 5-4 in the first set but a Krawietz double fault and Mies backhand error gave Salisbury, 28, and American Ram, 36, the chance to break back.
Their semi-final opponents will be decided at the O2 Arena on Friday.
Salisbury and Ram have gone though in second place in Group Mike Bryan and they will play the winners of Group Bob Bryan, which is currently led by Marcel Granollers and Horacio Zeballos.
Spain’s Granollers and Argentine Zeballos have won their opening two round-robin matches and face Jurgen Melzer and Edouard Roger-Vasselin at 18:00 GMT on Friday. Mate Pavic and Bruno Soares are the other possible opponents for Salisbury and Ram.
Earlier on Thursday in Group Mike Bryan, the already-qualified Dutchman Wesley Koolhof and Croatia’s Nikola Mektic ost 6-4 6-7 (2-7) 10-8 to Lukasz Kubot and Marcelo Melo.
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Group Mike Bryan
Pairing Matches won-lost Sets won-lost Games won-lost
1. Koolhof & Mektic 2-1 5-3 38-32
2. Ram & Salisbury 2-1 4-4 31-37
3. Krawietz & Mies 1-2 4-4 39-36
4. Kubot & Melo 1-2 3-5 32-35