After reaching the Pro Bowl as a rookie, he leads the Rams with eight tackles for loss and 13 quarterback pressures. He has 3.5 sacks this season, most among tackles who play in a 4-3 scheme.
''He's unblockable,'' Rams defensive end Robert Quinn said. ''You can double team him and he can split those. You try and single block him and he'll get a sack. He definitely helps me do my job. If he flushes a quarterback to me so I can make a play, I certainly won't be mad.
''I think when they found Aaron, they knew they found a special gem,'' he added.
The 6-foot-1, 285-pound Donald was the 13th overall pick last year, a decorated player out of Pitt. Donald led all NFL rookies with nine sacks. Now 24, he believes he is not only stronger, he has a better idea of what's going on in an NFL game.
He believes he can get better, too.
''The sky is the limit,'' Donald said. ''I worked my butt off in the offseason. I feel a lot more comfortable, a lot more prepared. I know what's going on. I know the concepts of the defense.''
Other teams are well aware of Donald, defensive coordinator Gregg Williams said.
''He's been outstanding and all of sudden he's learning about other team's giving him attention towards him,'' Williams said. ''When he first snuck into the league, a lot of people did not know a lot about him. Everybody knows about him now. You'll see schemes to him. You'll see game plans to him because people have to account for him all the time. He's so disruptive but he's a joy to coach.''
''He's not just a one-dimensional player,'' coach Jeff Fisher said. ''He is not just a pass rusher. He is a run defender. He is smart. He anticipates things. He can get on the edge. He recognizes formations. He's the complete player.''
''Since Fisher got here, he's been trying to build this team through the D-line,'' Quinn said.
NOTES: CB Janoris Jenkins (concussion) has passed all his tests, Fisher said, and is probable for Sunday's game against Cleveland. ... TE Lance Kendricks (thumb), WR Tavon Austin (hamstring) and RB Tre Mason (ankle) are all questionable while Quinn (knee) is probable. ... The last home game against Pittsburgh was delayed at the start when the pyrotechnics display caused a fire on the turf. Fisher said he believes there will be no problems but he quipped that he's ''seriously considering coming in the other tunnel.''