Karlovic and Berdych bow out
Steve Johnson claimed another notable scalp at the Citi Open in Washington after downing ninth seed Ivo Karlovic while Tomas Berdych was stunned by Vasek Pospisil.
Johnson defeated fifth seed John Isner in the previous round and he proved that was no fluke by knocking out veteran Croatian Karlovic.
The 24-year-old American had to do it the hard way though, losing the first set and then having to save two match points before claiming a 3-6 7-6 (7/4) 7-6 (9/7) victory and secure his place in the quarter-finals.
Men's top seed Berdych was stunned by world No 36 Pospisil, who bridged a 31-place gap in the rankings to triumph 6-4 6-4.
The Canadian sealed his third career victory over a top-10 opponent and will face Colombian 10th seed Santiago Giraldo, who eased past Victor Estrella Burgos 6-2 6-0, for a place in the semi-finals.
Wimbledon semi-finalist and second seed Milos Raonic edged two tie-breaks to beat former world No 1 Lleyton Hewitt and set up a quarter-final with Johnson.
The 23-year-old was strong on serve as he beat the 2004 winner 7-6 (7/1) 7-6 (7/3) and he was delighted with the battling qualities he displayed to book a place in the last eight.
"I was able to find my rhythm well at the end of each set. He made it difficult for me. The right attitude really got me through today in the key moments," he told www.atpworldtour.com.
Kei Nishikori overcame a second-set wobble to beat Lukas Lacko 6-2 2-6 6-3. He will face Richard Gasquet after the French number 14 beat Tim Smyczek 6-3 6-2.
There was no such shock for seventh seed Kevin Anderson, the South African needing just over an hour to beat Tunisian Malek Jaziri 6-3 6-4. Donald Young also managed to upset the odds to topple 15th seed Denis Istomin 6-3 3-6 6-3.
Upsets were also at a premium in the women's draw, with all three Russian seeds in action progressing through in straight sets.
Second seed Ekaterina Makarova saw off American Lauren Davis 6-2 6-4, fifth seed Anastasia Pavlyuchenkova downed Japan's Hiroko Kuwata 6-3 6-3 while Svetlana Kuznetsova, the number six, eased past Belgian Kirsten Flipkens 6-4 7-5 (7/5).
Makarova now takes on Pavlyuchenkova in the last eight while Kuznetsova meets Vania King, who came out on top in the battle between two Americans with a 6-1 6-3 win over Christina McHale.