After a terrible 2015 campaign, McLaren were upbeat with the P11 and P12 starting position of Alonso and Button at the start of the 2016 season. Alonso started on the supersoft tire and pitted on lap 12 onto the yellow marked softs. Esteban Gutiérrez, racing this year with newcomers Haas, was on a different strategy. Opting to stay out on the softs on which he started from P20, he found himself in front 7 seconds, directly in front of Alonso. So on lap 17, Gutiérrez was probably not expecting to keep the fast approaching McLaren behind, so my guess is he moved to the inside line, to decelerate early and wave him by. Interestingly, this was the first wheel-to-wheel fight of Gutiérrez in Formula 1 since 2014, so alternatively he was actively defending, but misjudged a suitable braking spot on the inside line. Either way, Alonso probably saw the move towards the inside line as a defensive action and tug in behind the Haas to gain the most advantage of the draft. With all his experience in Formula 1, he could make a good judgement where Gutiérrez would probably brake into turn 3. But Gutiérrez broke tens of meters earlier. Poor luck.
Aftermath
In the post-race interviews, Alonso and Guttierez agreed that it was a racing incident. The stewards agreed as well that ‘no driver was wholly or predominantly to blame’. Eventhough Alonso walked away from the crash feeling okay, doctors ordered Alonso to skip the next race at the Bahrain Grand Prix, two weeks after this crash. With scans revealing fractures and a small pneumothorax (collapse) on the lung, it was also doubtful if he could join the race in China two weeks after that, but he eventually did. The main discussion of this crash came two years later with the arrival of the halo.