I think that's the exact reason why RDA will beat him, that's how Chad Mendes had success against Conor.
Things to make note of though with regards to the Mendes vs McGregor fight is that Mendes was on very short notice, so wasn't in perfect shape, yet still had great success when fighting in close and on the ground. RDA is bigger, stronger and has shown great cardio in his fight with Pettis, I can't see him tiring like Mendes did. RDA is also a long time BJJ black belt, and a very accomplished overall grappler, I can't see Conor a threat to RDA on the ground, and I can't even see Conor getting out from underneath RDA should it go to the floor.
However, it's also worth noting that Conor had a serious injury going in to the fight with Mendes, so even he wasn't at 100%, how that impacted on his lack of ability to do anything from the bottom, other than eat elbows, is unknown.
The fight will be all about the distance and range that it's fought at, if Conor can keep the distance and RDA on the outside he will win the fight, if RDA can close the distance down and keep it fought on the ground or in the clinch it's going to be a long long night for Conor.