However, other than the odd feigned move and close encounters mid-corner, Spies was inch perfect to prevent Biaggi from ever getting into a position where he could prise away the race lead.
Battling it out until the very final corner, Biaggi had to settle for second position behind a delighted Spies, the American putting his race one devastation behind him as he celebrated across the line.
Behind Biaggi, who enjoyed his best World Superbike weekend in almost two years, Fabrizio was a close third having run out of laps to try and regain second from his fellow Roman.
Some distance back, Ten Kate Honda were once again the best of the rest, although the positions were reversed to have Jonathan Rea leading Carlos Checa
across the finish line.
Despite Spies' win, Haga can be happy to have emerged from the event still intact after another heroic performance in race two. Getting up inside the top ten from the start, Haga took on – and beat – Shane Byrne and Troy Corser
before holding off Tom Sykes to finish a fine sixth and protect some of his threatened lead overall. Haga now has more than a month to get back in full fitness for the final four rounds of the season.
Following his retirement in race one, Sykes recovered from a poor start to finish exactly where he started in seventh position, the Briton managing to fend off a hard charging Byrne and Jakub Smrz, the Czech rider being cheered on to ninth by his home crowd. Despite fading as the race wore on, tenth place Corser can nonetheless consider this to have been a breakthrough weekend for the BMW team.
Unable to match the pace of his team-mate, Aprilia's Shinya Nakano crossed the line in 11th position, ahead of Leon Haslam, who was another to fall away as the race progressed. Matthieu Lagrive, Ryuichi Kiyonari
and Lorenzo Lanzi
rounded out the points paying positions having benefitted from crashes for Makoto Tamada
and Yukio Kagayama, as well as a retirement for John Hopkins.