Kagayama's exit was typically more spectacular. The Japanese had taken the lead into turn one, but later dropped from the front group after running wide and through the gravel at the Lesmo corners. Kagayama rejoined safely, but was thrown spectacularly from his Alstare Suzuki soon after.
Two other big names to bite the dust were Max Biaggi and Carlos Checa. After a tough time in practice and qualifying, Biaggi had salvaged fifth in race one - a position he was battling to repeat in race two, until being torpedoed by Jakub Smrz at the second chicane with three laps to go. Worryingly, the Roman walked away holding his left wrist, which he broke earlier this year at Phillip Island.
Checa, who had qualified on the front row, finished eighth in race one after a poor start and got another tardy getaway in race two, sitting eighth at the end of lap one. The Spaniard then squandered the chance to gain points on Bayliss when he fell from the same position on lap 10.
Checa had earlier survived a heart-stopping moment when he was rammed from behind by Troy Corser under braking for turn one.
2008 race winner Fonsi Nieto steered clear of such incidents to finish fourth, having been in the lead group throughout. Michel Fabrizio was the sole factory Ducati to reach the flag in fifth, with Karl Muggeridge and Ruben Xaus sixth and seventh after failing to finish race one.
In the world championship standings, Bayliss remains 78 points clear of Checa, but Haga is now up to third - 82 points from the top - with Neukirchner just a single digit further behind.
Race results (2) - Monza: