FIRST ROUND LEADERBOARD:
-5 C Schwartzel (SA) -4 R Allenby (Aus), V Singh (Fij), E Els (SA) -3 J Senden (Aus), F Molinari (Ita), S Hansen (Den), JB Holmes (US), D Johnson (US), P Casey (Eng) Selected others: -2 P Harrington (Ire), L Donald (Eng) -1 P Mickelson (US) level I Poulter (Eng) +1 R Fisher (Eng) +2 L Westwood (Eng), G McDowell (NI) +4 R McGowan (Eng), R McIlroy (NI)
Casey dropped a shot at the last to slip back
England's Paul Casey stood two shots off the pace after the first round of the CA Championship in Miami.
Casey carded a three-under-par 69, while South Africa's Charl Schwartzel carded a 67 for the lead.
Ireland's three-time major winner Padraig Harrington is two under alongside England's Luke Donald.
Simon Dyson and Ian Poulter of England are level, while Northern Ireland's Rory McIlroy struggled to a four-over round of 76.
World number three and defending champion Phil Mickelson is four shots off the lead after a 71, five strokes better than playing partner McIlroy, the world number nine.
"I'm just struggling," said McIlroy. "I'm not playing well and just can't keep things going. I've been struggling since the weekend in Dubai [now more than a month ago]."
The 20-year-old has had back trouble in that time, but added: "That's not really a factor. I'm struggling with the whole game. When you're playing well it's easy, but when you're not it's difficult."
Australian Robert Allenby defied the windy conditions to reach eight under par after 12 holes, but by bogeying the last four for a 68 slipped one behind pacesetter Schwartzel at the World Golf Championships event.
Also on four under are Fiji's Vijay Singh and South Africa's Ernie Els, while world number two Steve Stricker, the highest ranked player in the 68-man field in the absence of Tiger Woods, is one over.
Casey, second and fourth on his last two starts and with a chance this week to go to second in the world for the first time, was satisfied with his round.
"I'm very happy with a 69 - and to be only two behind," he said. "Florida courses don't have a soft spot in my heart, but I like the challenge of this one."
Donald's opening two under par 70 in windy conditions was thanks in no small measure to holing out from the sand for a rare birdie on the 18th, the US Tour's second toughest hole last year.
Donald topped the "sand saves" category on the US Tour last season, and he said: "I've worked hard on it.
"I was pretty good at college, but when I came out on Tour I thought I was pretty average. I'd have given myself five or six out of 10 back then. Now I'm a nine."