Dimuth Karunaratne blamed a tweaked muscle for being run out on day four of the first Test between Sri Lanka and South Africa.
With the Proteas declaring on 406-6 before lunch in Port Elizabeth on Thursday, Sri Lanka were set a target of 488 for victory.
Karunaratne hit 43 off 113 balls but hesitated when Kaushal Silva called for a quick single, with JP Duminy's expert fielding resulting in him being dismissed as he came up short while diving at the striker's end.
The left-hander could have made it had he not stuttered, and he shouldered the blame after the tourists reached stumps at 240-5.
"It was all my mistake I think. Kaushal and I both play for the SSC [Sinhalese Sports Club], so we bat together and there's no misunderstanding," said Karunaratne.
"But I tweaked a muscle playing a reverse sweep earlier, and that was playing on my mind a bit. I stopped and tried to start again, and that's why I was run out.
"I did the hardest part in the earlier overs. I was beginning to see the ball well and then got run out and things were getting easier. The worst thing to do in a Test match is getting run out in a situation like that.
"I will have to start again in the next matches and survive the early overs again. But it's part and parcel of the game and there's nothing you can do."
However, Karunaratne believes Sri Lanka still have a shot at victory if Angelo Mathews (58 not out) and Dhananjaya de Silva (9 no) can emerge unscathed from the early exchanges.
"If we can get through the morning session, who knows - we could win this match," he added.
"For me, Kyle Abbott was the toughest bowler. He is quick and he moves the ball both ways. Vernon Philander also moves the ball both ways, but because he's a bit slower, he can be managed.
"But Abbott and Kagiso Rabada will be tough. If the batsmen can play them well, we have a chance."