Patience was key as Graeme McDowell upstaged Rory McIlroy and Tiger Woods with a grinding 69 in the Genesis Open at a firm and fast Riviera.

A lowly 219th in the world, winless since 2015, and coming off three successive missed, the 2010 US Open champion (38) knows he must wait for his moment to come to him as he seeks a return to golf's top table.

Patience is something McIlroy admits he needs to learn, especially on the west coast's treacherously fast and bumpy poa annua greens

"It is more of a mental test than anything else," McIlroy said of the greens after shooting a level par 71 to Woods' 72 and a 69 by Justin Thomas.

"I didn't pass that mental test last week at Pebble, so I am trying to stay a little more patient this week. 

"I hit some putts I thought we going in today that didn't quite, but at least I am hitting good putts so that's a positive."

After holing a bunker shot for an unlikely opening birdie at the driveable 10th and a 28-foot slider for eagle at his 10th to make up for "scrappy" bogeys at the 11th, 12th and 17th, he was pleased enough and eventually ended the day five stroke behind clubhouse leaders Patrick Cantlay and Tony Finau, who shot 66s to lead by one from Tom Hoge, Dominic Bozzelli and Sam Saunders.

“I struggled on the back nine, our first nine. I got off to a nice start and then missed the fairways on 11 and 12 and I was just a bit scrappy,” McIlroy said. “But I played a lot better on the front nine and gave myself a lot more chances. I didn't birdie any but I hung in there and even par is probably a fair reflection.” 

He added: “It was nice to take advantage of the easier holes, which I didn't do on the back nine. It should have been a couple of shots better but even par out there, it's a little tricky with the breeze, I am still in a decent position after today. 

Thomas shot a 69 to sit alongside McDowell on two-under as  Woods battled back from two-over after three holes to post a 72.

“It's nice to see him back inside the ropes,” McIlroy said. “He is going to play quite a full schedule this year.  His game looks good. He struggled early on again but hit some better shots and some really good drives coming in there. 

“If his body enables him to do what he wants to do, it's going to be an exciting year.”

Pádraig Harrington eagled the first but had to settle for a level par 71 as Shane Lowry hit just five fairways and shot 73 having cracked the face of his favourite driver last week

"I can imagine how tough this course would be with some rough as well," McDowell said after he went out in three-under 32 and dropped just one shot coming home. 

Woods agreed after mixing five birdies and four bogeys and a double-bogey seven at his second hole, the 11th, where he lost a wild drive in a eucalyptus tree.

"It's playing tough," said the 14-time major champion after hitting just seven greens, pointing out that while he made “a lot of birdie”, he made too many “silly” mistakes. 

"The greens are firming up, and that first hop is amazing, especially coming downwind,” Woods said. “But I fought back."

McDowell desperately needs a good week to boost his confidence, and he's confident it will come.

“I am. The year has got off to a slow start with a few missed cuts but I have been very positive about the way I am playing,” he said. 

“I really love what I am doing in practice and I feel like I turned the corner about six months ago. I really feel like I am ready to have some big tournaments.

"But in this game, you have to stay patient. You can't force it. And you can't want it. And you can't need it. I am trying to be really patient."

He got off to a lovely start, two-putting comfortably for birdie at the first before chipping in from 50 feet for a two at the 230-yard fourth.

He then saved par from eight feet at the fifth, rolled in a 12 footer for a birdie at the seventh and followed a lone bogey at the 13th with five closing pars.

As for McIlroy, the Holywood star managed to avoid three-putting but got little reward for some great ball striking.

Apart from that curling 28 footer for eagle, the longest putts he holed were a couple of four footers for par.

"I played a lot better on the front nine and gave myself a lot more chances. I didn't birdie any but I hung in there and even par is probably a fair reflection. 

"Tiger was hitting after me, and I said, 'I've finally found my range'," he said of his three at the first. "I'd missed a few from inside that before. So it was nice to get back to level." 

Harrington started by rapping in a 47-footer for eagle at the first but while he birdied the 10th, dropped shots at the fourth, ninth, and 15th saw him finish alongside McIlroy with a 71.

As usual, the short par-four 10th drew plenty of attention at 309 yards with the field averaging 4.11.

Woods and Thomas made birdies by laying up with irons and pitching close. But while McIlroy made birdie by holing that bunker shot, he could have made a big number having flared his three wood into the right rough, short-siding himself.

“I go for it on 10,” he told Sky Sports. “Looking at the stats for the last few years it looks like it averages about half a shot less by going for it than not. 

I think it's a no-brainer and I just hit a bad tee shot, flared it out right and had no shot to that tight pin. So I hit it in the bunker and the holed it. It was a nice way to start the day.”

As for the greens, he insisted the poa is “more of a mental test than anything else.”

He said: “You can only hit the ball on your intended line and try to hit it with good speed. It is not up to you after that. It is sort of up to gravity.”

The first round was suspended due to darkness at 5:48 p.m. (01:48am Irish time) with 12 players left to complete the round. 

While Jordan Spieth was tied for 36th with Harrington and McIlroy after a level par 71 - and 93rd for strokes-gained putting to McIlroy's 92nd - defending champion Dustin Johnson had a triple bogey seven at the fifth in a three-over 74.