The 19-year-old from Scotland won 26 of 37 first-serve points and blasted 31 winners to only 13 for the 109th-ranked South American, advancing to the third round of the US Open tune-up event after just 88 minutes in sweltering heat.

But Murray only managed a "C" grade in Gilbert's eyes.

"He said I played a tentative service game at 5-2 in the second set," Murray said. "I was maybe a little too defensive with the weather.

"Working with a new coach, it's always a little difficult. You always want to impress him. I was just glad to get through. I think he was grading me on the American scale."

Gilbert simply did not like how Murray finished off a match that should have come easier. Murray took the only break of the first set in the fifth game then broke Delgado four times in the second set but surrendered his own serve twice.

"He had his guy down and tired and let him back in a couple games," Gilbert said. "The best thing in life is to win with a C. That keeps you around in the tournament."

Murray, ranked a career-high 35 after a fourth-round run at Wimbledon, split with coach Mark Petchey last year and began working with Gilbert last week.

"The stuff we have done on the court has gone well. We have had fun off the court as well," Murray said.

"I doubt there is anyone better in coaching tactical-wise and that helped me out there, but as far as strokes it will take more than four or five days. I'm sure the week before the US Open we will get a lot of work in."

Gilbert, 45, has coached Andre Agassi and Andy Roddick to Grand Slam titles and world number one status. The retired US player signed a deal with Britain's Lawn Tennis Association to coach prospects, Murray prime among them.

"Everyone thinks I'm a magician -- I can just touch him and everything is going to be great," Gilbert said. "It's hard work. It takes time. It's methodical. It's just getting on the treadmill and going forward.

"He has to get a lot stronger and fitter. You can't get it in five minutes. It's going to take time. It's a journey for the rest of his career.

"He has to get better in a lot of areas. The two I see most are his serve and fitness. If he can get in the top 10 in service games held, you are going to see great things from Andy Murray."

Gilbert, who vowed to make Murray an early riser, has not started a morning workout before 11.

"He hasn't gotten me up too early so far," Murray said. "He wants to get me stronger. I realize I have to do that. I want to put the hard work in. I want to win a Grand Slam and you can't do that in the shape I'm in now."

Patience is tough when British fans and media have high expectations, especially when it comes to Wimbledon.

"You almost feel like they expect a little too much too soon," Murray said. "I didn't crumble under the pressure."

Gilbert had some advice about coping with the intense media spotlight.

"Last I checked they do it in every sport over there," Gilbert said. "Don't get caught up in what they say. Go have fun. Worry about what you are doing and results take care of themselves."