In common with fellow title hopefuls, and front row starters, Ui and Alzamora, Locatelli had to watch as some unexpected names came to the fore on the opening lap. Ui's Derbi team-mate Pablo Nieto was the first to show, sprinting from the outside of the front row to take the lead at turn one, to the obvious delight of the partisan crowd, and the Spaniard held sway until Locatelli completed his charge to the head of the field.
Second and third were initially held by Arnaud Vincent and Gino Borsoi, both coming through from behind the expected front runners, but neither Locatelli or Ui were to be denied. Alzamora, however, found himself dumped back to seventh on the opening lap, and struggled to make an impression from then on.
Once in front, Locatelli attempted to repeat his Mugello display by pulling away from Nieto and the fast-closing Ui but, despite eking out up to two seconds over his pursuers, never made the decisive gap that would have put the result beyond doubt prior to the last lap.
Instead, the Italian found himself coming under pressure from the unlikely shape of Masao Azuma. The Honda rider had qualified well - in sixth - but, along with his team, had expressed some doubt as to whether his tyres would be able to last the distance. The seemed to be little trouble in the early stages, however, as the Japanese gobbled up the two Derbis, and quickly ate into the gap that Loca had established.
By lap twelve, the leader's advantage had been reduced from 2.2secs to just 1.6secs and, three laps later, Azuma was in front, drafting past Locatelli down the start-finish straight and into turn one. The Italian, however, was prepared to play a waiting game and, having given Azuma his head for a lap, promptly replicated the move to reclaim top spot.
Azuma's ragged style then allowed the gap to yo-yo, as he missed apexes and ran wide on several corners, but the Honda's pace was not in doubt, and Locatelli had to keep his concentration right to the end as it recovered from the mistakes to repeatedly close the gap.
Only now closing in as Azuma and Locatelli diced, the two Derbis were embroiled in a scrap of their own. Although both riders knew that, in terms of the championship, Ui had to be allowed to lead over the line, Nieto was keen to prove the point that he was the faster of the two and, on lap 21, Ui eventually relented and allowed the Spaniard through.
The pair's attempts at using the faster man to draft up to the leaders was never likely to work, however, and Nieto dutifully ceded the advantage back to Ui with two laps to run to enable the Japanese to stay in touch in the standings.
Further back, though, Alzamora was forced to watch as his championship chances slipped away. Slow to recover from his poor start, the Spanish hero quickly found himself isolated in fifth, and appeared to be wrestling the Telefonica Movistar Honda at every turn. A forty-plus points deficit would seem to suggest that the reigning champion will not repeat in 2000.
Likewise, fellow Honda runner Mirko Giansanti will also be kissing goodbye to his title hopes, after a poor qualifying session left him in a position to be swallowed up by the rest of the grid after a particularly awful getaway. The young Italian found himself third from last going into the first turn and, despite battling back to 13th by the flag, will not have scored enough points to keep himself in contention.