Andy Murray survived some nervous moments to beat Mikhail Youzhny and reach the quarter-finals on another day of drama at Wimbledon.The second seed won 6-4 7-6 (7-5) 6-1 to make the last eight for the sixth year in a row at the All England Club.He is now the only Briton remaining in the singles after Laura Robson lost to Estonia's Kaia Kanepi on Court One, and will face Spain's Fernando Verdasco on Wednesday.Murray had arrived on Centre Court as the crowd were still digesting Serena Williams's surprise loss to Sabine Lisicki, but the Scot was not about to suffer a similar fate.He was in danger of being drawn into a lengthy battle in an edgy second set, but came through in the tie-break and wrapped things up after two hours and 37 minutes.A straightforward afternoon seemed to be unfolding when Murray played a terrific game that included a deft half-volley, a deadly backhand lob and a brilliant forehand pass, to lead by a set and a break.What followed was distinctly unimpressive, however, with his second serve coming under attack from the Russian 20th seed.When Murray double-faulted to drop serve for the second game in succession and then fell 5-2 behind, he was under real pressure for the first time in the tournament.Youzhny, playing in the last 16 at Wimbledon for the eighth time, had his chance to level when he served for the set, but after seeing off two break-back points he could do nothing about a Murray forehand on the third.The Scot was still searching for consistency, and another double-fault saw him change ends 4-2 down in the tie-break, but the most delicate of drop shots shifted the momentum.Murray cracked a cross-court backhand winner on set point and, after Youzhny received treatment on his shoulder, the third set was a one-sided affair. The Russian tamely handed over his serve in the second game and Murray broke for the fifth time before sealing victory with a blistering forehand and a serve-volley."It was a tough match, the first couple of sets especially, but once I got ahead in the third I concentrated hard on not letting him back in like I did in the second set," Murray told BBC Sport."I don't take anything for granted. I know how hard these tournaments are to win. There are no guarantees here and I don't come into them thinking I am going to win."I think a few rounds ago I was more nervous, but today I felt calmer before the match."I just concentrate on each game. Serena lost today; Roger has lost and Rafa has lost, so you cannot take anything for granted."