Murray has made it into his 10th quarter-final this season
British number one Andy Murray powered past Ernests Gulbis 6-4 6-2 to reach the St Petersburg Open quarter-finals.
Murray, seeking to follow up his Madrid Masters title success, broke the big-hitting Latvian twice in both sets.
The top seed maintained the impressive form which saw him begin the defence of his crown with an emphatic victory over Serbia's Victor Troicki on Monday.
The 21-year-old will now take on Janko Tipsarevic after the Serb defeated France's Jeremy Chardy 6-4 7-6 (7-3).
Murray broke Gulbis to take a 5-3 lead in the first set but then lost his own serve with the set up for grabs.
However, a second break, this time to love, saw the Scot take it 6-4.
The world number four survived an early scare in the first game of the second when Gulbis squandered a break point.
Murray held his nerve and broke Gulbis's serve at 30-40 in the sixth game to take a 4-2 lead.
He then held his serve and broke his opponent at the first time of asking in the eighth game to complete his victory.
"He is very unpredictable in his game style," said Murray. "He had a couple of good shots to break me, but I broke him in the next game, so it wasn't a problem.
"I'm going to try my best to win the tournament. When you keep winning, it gives you a lot of confidence."
Home favourite and eighth seed Marat Safin crashed out with a shock 6-4 6-2 defeat by Kazakhstan's Andrey Golubev.
Safin, a two-time winner of the tournament, had trouble with his serve and 150th-ranked Golubev took full advantage to reach his first career quarter-final.
"He had nothing to lose and played with no problems. No matter how I tried, it was his day today," said Safin.
Victor Hanescu of Romania beat Kazakhstan's Mikhail Kukushkin 6-3 7-6(7), while fourth-seeded Russian and 2004 champion Mikhail Youzhny fell to German qualifier Mischa Zverev 7-5 6-4 in the last match on centre court.
The Moscow-born Zverev now meets Golubev in Friday's quarter-finals.