On a day when ex-BMC teammate Tejay van Garderen retained yellow by tailing stage winner Kasper Asgreen across the line, Porte finished among a group of 11 riders 31 seconds off the pace.

In just his second day of racing after a six-week layoff, Porte was largely happy with his performance on the Rancho Cordova to South Lake Tahoe stage, which climbed 4420 metres over 214.5km.

"It was definitely long but it wasn't so hard until the final there, but when you're racing up around 2600m you don't have to be going fast for it to be hard," Porte said on Twitter.

"I think it was a pretty good day today, we were a little bit on the back foot, we had to ride when we wouldn't have liked to have ridden but there's some really strong teams here.

"The next couple of days are hard stages as well ... for me personally it's just nice to be back in the racing."

The week-long event finishes on May 18.