The French underlined their championship credentials with a 35-17 victory in Paris on Saturday, crushing Ireland's brave resistance with a performance which suggested they had plenty left in the tank.
But tries from Anthony Foley and Tyrone Howe proved that Eddie O'Sullivan's men also had much to offer as an attacking force, with D'Arcy providing his side with their greatest cutting edge.
The Leinster centre went close to scoring early in the match - his opposite number Yannick Jauzion just managed to snuff out the danger - and set up Howe's 70th-minute touchdown with a superb off-load.
Strong, quick off the mark and elusive in the tackle, D'Arcy proved the ideal replacement for his provincial team-mate Brian O'Driscoll and marked his first international start in fine style.
But with O'Driscoll nearing full fitness after missing out against France because of his hamstring injury, D'Arcy could find himself relegated to the bench when championship hostilities resume against Wales.
And although O'Sullivan is sure to try and accommodate the 24-year-old back somewhere in his starting line-up - either at wing or full-back - D'Arcy is bracing himself for the worst.
"Brian is the star and captain of the squad. I've been filling in for him at Leinster and on Saturday I did the same job for Eddie with Ireland," he said after finishing as the game's leading ball-carrier.
"When Brian comes back and I'm forced to drop to the bench, or even if I'm not selected in the final 22-man squad, it's not the easiest pill to swallow. But I will just have to get on with it.
"The possibility of me playing in another position is down to Eddie. I've been around long enough to know that if I don't get picked, it's purely selection. If it doesn't go my way then I'll go back to Leinster and hopefully help them to a few victories."