Alexander Waske and Philipp Petzschner beat Dmitry Tursunov and Mikhail Youzhny 6-3, 3-6, 7-6, 7-6 in the doubles to put Germany 2-1 up on holders Russia in their Davis Cup semi-final on Saturday.
The Germans had to overcome an elbow injury to Waske in the fourth set before prevailing in just under three hours.
"I thought the match was over," said Waske, who was forced to pair up with Cup debutant Petzschner after regular doubles partner Michael Kohlmann suffered a knee injury. "I felt something just snapped in my elbow.
"It was hurting like hell and I was close to quitting but it was so important to keep going," he told reporters. "Philipp just played great, first time in the Davis Cup and what a performance. If I had a hat, I'd raise it."
Waske and Petzschner, ranked 206th in singles and 262nd in doubles, were playing together for the first time but it was the Russians who looked out of synch for most of the match on the clay of the Olympic sports complex.
"They just played better as a team," a dejected Youzhny said.
"Rankings don't mean much in Davis Cup," added Tursunov. "It was evident we didn't play well together. Maybe we need a set of twin brothers to have a good doubles team."
The Germans broke Youzhny and Tursunov to take the opening set before the hosts returned the favour by breaking Waske twice in the second.
The visitors took the third-set tiebreak 7-4 before Waske hurt his right elbow while serving in the third game of the fourth set.
He called for a medical time-out but eventually decided to continue.
The Russians tried to put more pressure on Waske by hitting to his side of the court but the Germans held their nerve to secure the tiebreak 7-5.
"I didn't believe we would win this," said Waske, 32.
Petzschner, 23, said: "Our captain Patrick Kuehnen just kept telling us we were stronger than them, stronger in our head and in our spirit."
Russia must now take the two reverse singles on Sunday to reach the final for the second year in a row.
World number four Nikolay Davydenko faces Germany number one Tommy Haas before claycourt specialist Igor Andreev meets Philipp Kohlschreiber.