#2 Bottas has a mechanical failure
Mercedes had an almost flawless record in 2017 with only one DNF, when Bottas fell victim to an engine failure in Barcelona. However, in 2018 their record has not been so good. Hamilton and Bottas both saw the wrong end of a mechanical failure in Austria, forcing a double DNF. Then in Qualifying in Germany, Hamilton's car suffered a Hydraulic failure that relegated him to P14 on the grid, although the Brit powered through in the race for a stunning victory.
That said, 2018 has shown that Mercedes is not completely perfect and like other teams are susceptible to hardware issues. Whether it be in Qualifying like Lewis last weekend, or in the race as in Austria, we believe that the weekend will be spiced up by Bottas having a mechanical failure of some sort. It certainly wouldn't be out of character for the Finn, who has been having seriously bad luck this year.