BEIJING, August 15, 2008 (AFP) - The US swimmers tasked with booking a spot for Michael Phelps in the 4x100m medley relay final on Friday admitted they weren't taking any chances.

'We just needed to get the 'A' guys in a good spot,' said backstroker Matt Grevers, who led off the quartet.

'We got the job done, we had safe starts, that was the goal, safe starts, no DQ (disqualification) for no reason.

'We've heard those words a lot. I don't think we'll be allowed to leave China if we get a DQ.'

Even with the safety-first approach, the United States posted the top qualifying time of 3:32.75.

'There was anxiety,' added Grevers, who was especially careful on his underwater starts, which can't exceed 15 metres.

'I was telling myself 'don't go past 15 metres', 'don't go past 15 metres' and the other guys off the blocks 'don't go early off the blocks'.'

Grevers said that he, Matt Gangloff, Ian Crocker and Garrett Weber-Gale were acutely aware that the medley relay final on Sunday could see Phelps going for a record eighth gold medal at one Games.

'This relay might be all it comes down to,' Grevers said. 'It's a historic event and this relay could be the one for the eighth gold and you don't want to be the one to screw that up for him.'

Like the rest of the US team - and swimmers from around the world, Grevers is in awe of Phelps.

'He's unreal, I never thought I'd see that kind of swimming. It'll be one for the ages, in 100 years everyone will remember this Olympics, what Michael did, or hopefully does.'

Crocker remembers all too well what it was like when he botched a changeover to get the United States disqualified in the medley relay at the world championships in Melbourne, costing Phelps a likely eighth title there.

'I wasn't going to push it,' he said. 'Unfortunately, I remember last year. It's hard hard to forget about that.

'After this week, all that Phelps has done, you don't want to be the guy who stood in his way, do something stupid. I want him to have every shot at doing it.'

Of course, Crocker would be happy to thwart Phelps by doing something right - in the final of the 100m butterfly on Saturday.

World record-holder Crocker said Serbian Milorad Cavic could also pose a danger to Phelps.

'People point at me, but Cavic is looking good and it'll be a tight race,' Crocker said.