McIlroy only added the event to his schedule at the 11th hour after struggling to adapt to new equipment and recapture the form which brought him five wins in 2012, including a second major at the US PGA Championship.
But with caddie JP Fitzgerald advising him that he needed more competitive rounds under his belt, McIlroy travelled to San Antonio and carded an opening level-par 72 to lie five shots behind Matt Bettencourt, who carded a 67 to overtake long-time clubhouse leaders Padraig Harrington and Billy Horschel.
Starting from the 10th on the difficult Oaks Course - the fourth most difficult on the PGA Tour last year - McIlroy opened with four pars before picking up a birdie on the par-five 14th and another on the short par-four 17th.
However, a bogey on the 18th after finding the water was the first of three in succession which dropped him back to one over par, not what the world number two was looking for after speaking of the need to cut out "silly mistakes" in his rounds.
The 23-year-old stopped the rot with pars at the third and fourth and then birdied the next two holes after pitching to five feet each time, but carded his fourth bogey of the day on the ninth.
Three-time major winner Harrington had also bogeyed his final hole, the 18th; the only blemish on his card caused by three putts from 35ft.
The 41-year-old won the Open Championship in 2007, successfully defended it the following year and then won the US PGA Championship a few weeks later, but has not tasted victory on one of the major tours since - his last win came on the Asian Tour in 2010.
Harrington admitted he had enjoyed his fair share of good luck in cold and blustery conditions, with his only bogey caused by three-putting the 18th.
"It was cold and that really does affect the ball," the Dubliner told reporters. "I didn't have a great ball-striking round but my misses were either in the right places or I got slightly fortunate and then got up and down.
"I'm not walking away from this round thinking 'wow, I hit a number of pure golf shots', or anything like that. It was more mental fortitude than ball striking.
"This morning, early on, it was a battle of survival. Last week back in Ireland it was snowing and I didn't feel this cold. There was a feeling of 'let's just hang in there and stay in the tournament'. Sometimes that lets you play a little bit more within yourself."
Anyone winning this week will have to defy the odds if they want to also claim a Green Jacket at the Masters, however.
Only two players have won the week prior to the Masters and then gone on to win in Augusta; Sandy Lyle in the Greater Greensboro Open in 1988 and Phil Mickelson in the BellSouth Classic in 2006.