South Africa's Ernie Els insists his Houston Open campaign is all about this week's US PGA Tour event, and he can't afford to chase a victory for the sake of booking a Masters berth. Els must win here to qualify for the first major of 2012, which starts a week later in Augusta, Georgia. Although he hasn't missed the Masters since 1993, Els said it would be counter-productive to focus on that in Texas. "You can't go into a week putting pressure on yourself to win to get into another week," Els said. "I just want to have a good week. If I can win, obviously, that would be absolutely wonderful. But my goal here is not to get into the Masters, it's to play the Houston Open as good as I can. "If I get into the Masters, that's great. If I don't, then I've had many Masters that I can look back at, and I'll get back in there next year." Els, owner of three major titles, posted top-five finishes in Palm Harbor and Bay Hill in recent weeks. Even so, he has already resigned himself to missing the Masters. "It'll be a very weird feeling," Els said. "Since I've been a professional at this level, I've played at the Masters, so it'll be a very weird feeling not to be there. I'll miss it." Tournament officials could still offer a special invitation to Els, but he said he wasn't expecting it. "It is an invitational event," he said, "and they have their reasons to invite somebody or not, and that's the sad part. I'll probably miss it for the first time in 18 or 19 years. My streak will come to an end, unfortunately. "I can't blame the Masters people for not inviting me. I've put myself in this position by not playing very well." Houston's bid to boost its stature as a Masters prep event -- with light rough and fast greens to simulate typical Augusta National conditions -- has again drawn a strong field. World number three Lee Westwood of England, Ireland's Padraig Harrington and Northern Ireland's Graeme McDowell -- runner-up to Tiger Woods at Bay Hill on Sunday -- are on hand, as is defending champion Phil Mickelson. "They really go the extra mile with the details," said McDowell, who is playing here for the first time since 2006. "It's a nice test, without being too difficult." Mickelson, who practiced at Augusta National this week, was expected to arrive on Wednesday. He has played here every year since 2008 and said the layout at Redstone offers some aspects in common with Augusta but plenty of differences. "There's water constantly pinching in the fairways and there's no chipping areas," said Mickelson, who will play the first two rounds with defending Masters champion Charl Schwartzel and Fred Couples. "You're either in the bunker, or in water. There are no chipping areas around the course to help you prepare for the Masters, so it's really not that great."