Fourth seed Wade Johnstone crashed out and two qualifiers prevailed in the first round of the Betty F Griffin Memorial Florida State Open on an opening day of shocks in the PSA World Tour Challenger 10 squash event at Lifetime Athletic Club in Boca Raton, Florida, USA.

Unseeded Pakistani Yasir Butt produced the biggest upset when he despatched fourth-seeded Australian Johnstone 11-8, 11-7, 10-12, 11-7.

The world No71 from Lahore will now face qualifier Peter Creed following the Welshman's marathon 11-5, 12-10, 12-14, 11-9 victory over higher-ranked Englishman Anthony Graham in 90 minutes.

Egyptian Karim A G A Samy also claimed a surprise quarter-final berth. The 22-year-old qualifier from Cairo overwhelmed Clinton Leeuw, a South African ranked more than 20 places higher, 2-10, 11-7, 5-11, 11-8 in 55 minutes.

But top seed Miguel Angel Rodriguez needed only 37 minutes to register his place in the last eight. The world No36 from Bogota defeated Frenchman Fabien Verseille 11-5, 11-0, 11-7 and will now face Dutchman Dylan Bennett for a place in the semi-finals.

Title-holder Alfredo Avila will not be on the winner's podium for the second year in a row. The 20-year-old Mexican who upset the top seed en-route to success in the event last year, battled for 70 minutes against Kamran Khan - but it was the third-seeded Malaysian who triumphed 11-8, 11-9, 12-10 to reach the quarter-finals.

RESULTS: PSA Challenger 10 Betty F Griffin Memorial Florida State Open, Boca Raton, Florida, USA

1st round:
[1] Miguel Angel Rodriguez (COL) bt Fabien Verseille (FRA) 11-5, 11-0, 11-7 (37m)
Dylan Bennett (NED) bt [Q] Geoffrey Demont (FRA) 11-3, 11-2, 11-7
[Q] Peter Creed (WAL) bt Anthony Graham (ENG) 11-5, 12-10, 12-14, 11-9 (90m)
Yasir Butt (PAK) bt [4] Wade Johnstone (AUS) 11-8, 11-7, 10-12, 11-7
[3] Kamran Khan (MAS) bt Alfredo Avila (MEX) 11-8, 11-9, 12-10 (70m)
Erik Tepos Valtierra (MEX) bt [Q] Tom Pashley (ENG) 11-5, 11-8, 7-11, 11-4 (38m)
[Q] Karim A G A Samy (EGY) bt Clinton Leeuw (RSA) 12-10, 11-7, 5-11, 11-8 (55m)
[2] Yann Perrin (FRA) bt Joan Lezaud (FRA) 8-11, 11-4, 11-9, 11-5 (60m)

Quarter-final line-up:
[1] Miguel Angel Rodriguez (COL) v Dylan Bennett (NED)
Yasir Butt (PAK) v [Q] Peter Creed (WAL)
[3] Kamran Khan (MAS) v Erik Tepos Valtierra (MEX)
[2] Yann Perrin (FRA) v [Q] Karim A G A Samy (EGY)

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