Former champion Tommy Haas of Germany advanced with a 6-4, 6-4 win over Australia's Wayne Arthurs in searing 114 degree Fahrenheit heat at the University of California Los Angeles courts.
Hewitt, who ended an 18-month title drought at last month's Stella Artois tournament and was playing his first event since Wimbledon, dropped serve four times against Goldstein, whom he beat in the Las Vegas semi-finals in March.
"I just struggled after a couple weeks off," the 2002 Wimbledon champion said. "He played solid. He's a guy you've got to go out and beat every time out."
Haas, who beat compatriot Nicolas Kiefer in the 2004 Los Angeles final, did not face a break point against the big-serving Arthurs and dropped only six points on his own serve.
"I was really playing solid and not making too many loose mistakes," Haas told reporters. "I thought I was solid on both wings."
The German, who claimed hardcourt titles in February at Delray Beach and Memphis, will meet Chile's Paul Capdeville in the next round.
Double grand slam champion Marat Safin cashed in on poor serving by American Mardy Fish to win their first-round encounter 6-4, 7-5.
Chasing his first singles title since the Australian Open 18 months ago, the Russian converted three of nine break points to maintain the upper hand.
Safin was in relatively optimistic mood, his battle for form this season having reached a new low last week when he was beaten in straight sets by the 512th-ranked Wesley Whitehouse at the RCA Championships in Indianapolis.
"I had one week to practise and managed to improve my fitness and get some rest," the former world number one said. "I'm much better. For the first round, this was pretty good."
Safin, who beat Roger Federer en route to last year's Australian Open title and outclassed Pete Sampras at the 2000 U.S. Open, next meets third seed Fernando Gonzalez of Chile.
In other first-round matches, seventh-seeded Slovakian Dominik Hrbaty knocked out American Zack Fleishman 7-5, 7-5, Swiss qualifier George Bastl beat Frenchman Nicolas Mahut 6-3, 7-6 and German Lars Burgsmueller scraped past American lucky loser Michael Yani 6-4, 3-6, 6-3.
Robby Ginepri beat Justin Gimelstob 6-4, 6-4 in an all-American clash to complete the day's play.
Top seed Andy Roddick begins his campaign against South African Rik de Voest on Wednesday, the American's first match since announcing that Jimmy Connors was to be his new coach.
