While attempting to get at Vikings quarterback Joe Webb, Matthews was blocked very well by Matt Kalil. Matthews ended up on the ground, but still notched the sack because Webb tripped over him. The Vikings lost nine yards on the "sack."
That wasn't the end of Matthews' domination of Webb, who started for the first time this season because of an injury to Christian Ponder. Later in the game, Matthews continued to ruin Webb's trip to Green Bay. Matthews managed a sack, forced fumble and fumble recovery on one play.
Matthews started the season hot, getting six sacks in his first two games. Injury slowed him down midway through the season, but it looks like he is getting hot again at the exact right time for Green Bay.