Taylor Fritz and Tommy Paul fired USA to the top of Group D in their bid to reach the Final 8 at the Davis Cup by Rakuten Finals, securing victory over Kazakhstan ahead of the doubles.

With Paul putting on a dominant display against Mikhail Kukushkin in an opening 6-1, 6-4 victory, Fritz battled past Alexander Bublik 7-6(6), 1-6, 6-3 in the battle of the No.1s to secure the Americans’ second win in as many days in Glasgow.

Bublik retuned with Aleksandr Nedovyesov to collect a second fine doubles win of the week, beating Jack Sock and Rajeev Ram 6-2, 7-6(6) after downing Dutch pair Wesley Koolhof and Matwe Middelkoop on Tuesday, leaving the final score 2-1 to the Americans.

While the fates of both nations remain unknown – at least until Netherlands takes on Great Britain on Friday – USA are in good shape to advance having posted two wins before facing Netherlands on Saturday, while Kazakhstan knows it is win-or-bust when it faces Great Britain on Sunday.

“We had another great one today,” said Bryan. “We'd have loved to finish it off with the doubles, but we came a little sluggish and those guys capitalised.

“Tommy has been phenomenal. He's moving so well it's almost impossible to hit a winner on Tommy right now. And I thought Taylor bounced back incredibly from yesterday's heartbreaker. He got really blown out in the second set and was able to shift the momentum, which is not easy to do.”

We'd have loved to finish it off with the doubles, but we came a little sluggish and those guys capitalised

World No.12 Fritz has found Bublik a tricky opponent in the past, and it was the world No.44 who looked set to move ahead when he broke to love for a 4-3 lead. But Fritz hit back with Bublik serving for the opener, saving three set points to level up at 5-5, and a fourth in the ensuing tiebreak.

Bublik showed just what he is capable of with a quickfire second set, underscoring the problems his power and variety can cause with a string of blink-and-you’ll-miss plays that left Fritz shaking his head at times.

But in the decider the American stole an early break that proved decisive, denying Bublik a look at a break point to close out victory after one hour, 36 minutes.

“Yesterday, I lost but I felt like I played well – I felt like I was, for the most part of the match, the better player and I just didn't capitalise on some opportunities I had," Fritz said. "Today I think a lot of it was just accepting in a third set that I was just going to have to battle and grind and play longer rallies. My game style is to be very aggressive and dictate. I just had to sit back and be a little bit more patient and I think that's what got it for me in the end."

Tommy Paul (USA)

Tommy Paul

Earlier, world No.29 Paul picked up where he left off 24 hours earlier at the Emirates Arena, collecting his second Davis Cup win against Kukushkin. As he had against Great Britain’s Dan Evans, Paul won the points that mattered in an opener that was tighter than the scoreline suggests before breaking early in the second set.

Ever the fighter, Kukushkin began to see his hard graft rewarded, albeit too late to affect the result – a break to level up at 4-4 was immediately given up in the next game, and Paul served out for victory after one hour, 25 minutes.

"I felt pretty comfortable, even though the games were close," Paul said. "The first set I felt like I was in full control. He wasn't putting too much pressure on me, so I felt like I could dictate everything in the first set. The second set got tricky."

Group D results and standings