But after the Dolphins were stopped on fourth-and-3 six minutes into the second quarter, Lucas returned to the sidelines and sat on the bench.
That's when his back stiffened up.
"I was just nervous," Lucas said. "That's never happened to me. It was just weird."
Lucas said he is now perfectly fine, but regretted having had his evening against the Rams cut short.
"I really wanted that two-minute drill," he said. "I would have (liked to have) played the whole game, to be honest."
While he was in the game against the Rams, Lucas looked sharp as he completed 5 of 6 passes for 45 yards and also scrambled twice for 11 yards.
He also was in the game when the Dolphins scored their only touchdown.
The Dolphins had gotten a first-and-goal at the St. Louis 2 when Lucas replaced Fiedler at quarterback. While many might have anticipated the Dolphins sending Lucas on a rollout, he simply handed off to Lamar Smith, who bulled his way into the end zone.
When asked whether fans should get used to seeing him in the game in goal-line situations, Lucas didn't give anything away.
"That might be something we're doing; it might not be," he said. "You better be ready for anything."