PORTRUSH, Northern Ireland — If you weren’t expecting a lot out of Tiger Woods in the first round of the British Open on Thursday after he opted not to play a tournament since the U.S. Open last month, you got exactly what you figured you would get: a lackluster performance during which he looked anything but sharp.

Woods shot a 7-over-par 78 at Royal Portrush, and he’ll have to post a low number in Friday’s second round to make the cut and stick around for the weekend. If he misses the cut, it will be the same result he had in the PGA Championship at Bethpage after opting not to play a warmup tournament after the Masters.

The 78 was Woods’ second-highest score in a British Open, outdone only by the 81 he shot in torrential rain and wind in 2002 at Muirfield.

Afterward, the 43-year-old Woods sounded very much like someone conceding to his age and physical liabilities.

“It’s just Father Time and some procedures I’ve had over the time,” he said. “Just the way it’s going to be. One of the reasons why I’m playing less tournaments this year is that I can hopefully prolong my career and be out here for a little bit longer.”

Asked whether he would play Friday, Woods said, “I’ll be there.”

“It’s going to be a lot more difficult,” he said. “I’m not 24 anymore. Life changes, life moves on. And I can’t devote the hours to practice like I used to: standing on the range, hitting balls for four or five hours, go play 36, come back, run four or five miles and then go to the gym. Those days are gone, OK?

“I have to be realistic about my expectations and hopefully peaking at the right time. I peaked at Augusta well. And hopefully I can peak a few more times this year.”

TV cameras caught Woods grimacing after his opening tee shot, leading to speculation that his back was hurting him.

Asked if he was in pain, Woods said, “I’m sore, yes. I’m just not moving as well as I’d like. And unfortunately, you’ve got to be able to move, and especially under these conditions, shape the golf ball. And I didn’t do it. I didn’t shape the golf ball at all. Everything was left-to-right. And wasn’t hitting very solidly.

“I’m going to have days like this, and (I’ve) got to fight through it. I fought through it. Unfortunately, I did not post a very good score.”

Asked what the difference was for him at Augusta, Woods said, “For some reason, I found something in my golf swing that allowed me to start shaping the golf ball high and draw the ball again. And once I found that playing that golf course, I felt comfortable.”

He has looked anything but comfortable since, and Thursday’s round was a low point.