Henman bows out in Miami

Henman was in obvious pain from the outset

Click here for Tuesday's results from Miami

Tim Henman has been forced to retire from the fourth round of the Nasdaq-100 Open Masters in Miaimi with a neck injury.

The British number one conceded his match to Roger Federer having lost the first set 6-2.

Henman originally damaged his neck leaving the players' locker room ahead of his contest against Felix Mantilla in the previous round.

And, although he beat the Spaniard 7-5 6-4, he was continually hampered by the problem against Federer.

Agassi is hoping to match his wife's title haul

From the outset of Tuesday's match, the British number one was clearly in pain.

Unable to serve properly, he was broken for the first time to go 4-2 down and, despite treatment from the trainer, he conceded defeat after losing the first set.

Afterwards Henman said: "When I woke up this morning it was pretty uncomfortable and I wasn't really sure whether I would play at all when I came to the courts.

"Then I hit some balls and I was a little more optimistic but, then when you've got to move and with the jarring, it was pretty evident I couldn't play."

Elsewhere on court, Andre Agassi halted ATP Champions Race leader Thomas Johansson with an impressive 7-5 6-2 win.

The former world number one broke Johansson's opening service game and, from there, continued his court domination in the searing heat.

Gaudio injury

Agassi is bidding to match wife Steffi Graf's record of five Miami Masters titles this week.

The American revealed the secret of his success after the win.

He said: "You go out there with a healthy respect for somebody that's won the first slam of the year. It's an opportunity to raise your game."

Also through to the quarter-finals was 20th seed and Miami resident Nicolas Lapentti, who produced a popular result when he defeated Adrian Voinea 6-2 3-6 6-3.

Henman was not the sole fourth-round withdrawal, Gaston Gaudio also bowed out of his all-Argentine clash with Juan Ignacio Chela due to injury.

Top-seeded Lleyton Hewitt needed only 10 minutes on Wednesday to complete a rain-interrupted 6-4 6-1 victory over American James Blake.

Hewitt led 3-1 in the second set on Tuesday when the match was suspended. He broke Blake's serve six times, including twice Wednesday to complete the fourth-round victory.

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Tuesday's men's results:

Andre Agassi (USA x9) bt Thomas Johansson (Swe x8) 7-5, 6-2
Roger Federer (Swi x12) bt Tim Henman (Gbr x5) 6-2 retired
Nicolas Lapentti (Ecu) bt Adrian Voinea (Rom) 6-2, 3-6, 6-3
Juan Ignacio Chela (Arg) bt Gaston Gaudio (Arg) 6-1, 5-7, 4-3 retired
Lleyton Hewitt (Aus) bt James Blake (USA) 6-4, 6-1