* Hewitt defeats third seed Del Potro in quarter-finals
* Top seed Murray to face Tsonga in semi
* Defending champion Cilic sees off Berdych (Adds late matches)
LONDON, June 14 (Reuters) - Something about the lawns of London bring out the best in Australian veteran Lleyton Hewitt and he gave a glimpse of the grasscourt arts to beat Juan Martin del Potro in Friday's quarter-finals of the Aegon Championships.
The 32-year-old mixed skidding slices, sharp volleys and accurate serving to keep powerful third seed Del Potro under wraps in a 6-2 2-6 6-2 victory on a sun-splashed centre court at Queen's Club, ending the match at a gallop.
The former Wimbledon champion and world number one and four-times Queen's Club winner will face Croatia's Marin Cilic in the last four after the defending champion beat second seed Tomas Berdych 7-5 7-6(4).
Top seed Andy Murray continued his quest for a third Queen's title with a 6-4 7-6(3) defeat of Germany's Benjamin Becker.
Briton Murray, who missed the French Open with a back injury, trailed 4-2 in the second set but found an extra gear to subdue the 31-year-old and set up a semi-final against France's Jo-Wilfried Tsonga who beat 20-year-old American Denis Kudla in straight sets.
"Jo plays a pretty all-court game. He comes in to net more than most of the players. He's a tough player to play," world number two Murray, who will have to cope with the usual pre-Wimbledon hype in the coming weeks, told reporters.
Hewitt, bidding to become the oldest player to win the traditional pre-Wimbledon warm-up tournament, dominated the first set but Argentine Del Potro found his range with some thumping groundstrokes to square the match.
Unseeded Hewitt never panicked though and took charge in the fourth game of the decider, breaking Del Potro to love and then holding to love to establish a 4-1 lead.
He finished the match with a classic approach shot and volleyed winner before punching the air.
"I was a bit scratchy in the first match and haven't really put a foot wrong since," Hewitt, who is second only to Roger Federer for match wins on grass amongst active players, told reporters. "The second set he played incredible tennis."
Hewitt has been plagued by hip, foot and ankle injuries in recent years, is 82nd in the world rankings but remains a class act, especially on grass.
"I love playing as many weeks on grass as possible," said the father of three.
"Yeah, that's why the Olympics and playing Newport last year was so special to me because I could play a bigger chunk of tournaments. I think it's a unique surface.
"There are certain players that play really well on it." (Reporting by Martyn Herman, editing by Pritha Sarkar and Alison Wildey)