Sock, Isner reach last eight in Houston

The seeds enjoyed a good day at the US Men's Clay Court Championship, with Jack Sock and John Isner among them.

Sock, the top seed at the ATP 250 event in Houston, overcame German veteran Tommy Haas 6-4, 3-6, 6-3.   -  Getty Images

Jack Sock and John Isner came through testing second-round matches to reach the US Men's Clay Court Championship quarter-finals.

Sock, the top seed at the ATP 250 event in Houston, overcame German veteran Tommy Haas 6-4, 3-6, 6-3.

The American is enjoying an excellent 2017 and moved into his fifth quarter-final of the year with victory in just under two hours.

Awaiting Sock – the 2015 champion and last year's runner-up – in the last eight is Feliciano Lopez, who got past Chung Hyeon 4-6, 6-2, 6-1.

Isner progressed with a hard-fought 6-7 (5-7), 7-6 (7-3), 6-3 win over Argentine qualifier Leonardo Mayer.

The American second seed, winner in 2013, sent down 20 aces to reach the quarter-finals.

Isner will face Ernesto Escobedo, the American wildcard having beaten Brazilian Thiago Monteiro 4-6, 6-4, 6-4.

The seeds enjoyed a good day as Steve Johnson, Fernando Verdasco, Sam Querrey and Thomaz Bellucci also won through.

Johnson edged past Dustin Brown 7-6 (14-12), 6-4 to set up a clash against Verdasco, who was too good for Nicolas Kicker 7-6 (7-4), 6-1.

Querrey, a two-time runner-up, beat Horacio Zeballos 6-4, 6-4 and next faces Bellucci after the Brazilian had a 2-6, 7-6 (7-5), 6-2 win over Maximo Gonzalez.