Massa , sixth in this year 's championship , will remain alongside Valtteri Bottas at Williams .
Massa , sixth in this year 's championship , says the squad 's competitiveness in 2016 will determine whether he will stay in the sport into 2017 .
Massa , sixth in this year 's championship , will remain alongside Valtteri Bottas at Williams but says the squad 's competitiveness in 2016 will determine whether he will stay in the sport into 2017 .