Lions boost as Farrell declared fit
Farrell suffered a quadricep strain at training on Thursday and sat out the Lions' win over the Maori All Blacks on Saturday.
But Gatland said his absence was precautionary and the Englishman was ready to play.
"Owen could have played on Saturday. Had it been a Test match he would have played," he told reporters.
"We just made a decision that it wasn't worth taking that risk.
"It's a quad strain that was very high and not on his kicking leg. It's on his left leg. I've no doubt he will be 100 percent fit."
Farrell is regarded as a near-certain selection against the All Blacks at Eden Park, either at flyhalf or inside centre.