It’s been almost three weeks since the Lions rookies were allowed (by NFL rules) to join the veterans for OTAs.

The first few days were a little spotty which was to be expected since even the best college players have to learn how NFL practices are run.

On Thursday the rookies — draft picks and undrafted free agents — proved that they are fitting right in.

“I think today you would have a hard time, if you didn’t have a roster and you didn’t know the team, of looking out there and seeing who the rookies were,’’ coach Jim Schwartz said on Thursday. “... They’re in much better condition, they’ve adapted quickly. They know what to do, it’s not a fire drill when they’re out on the field.’’

Thursday was the Lions’ last OTA until June 21 and 22. Those two OTAs will be followed by a three-day minicamp. Then they will break until training camp opens the end of July.

(Follow me on Twitter @PaulaPasche.)