They could both score at the opening game

Russia didn't have a fairly good performance at friendly games. In fact they have been inactive for a long time since their last official games were almost a year ago at the Confederations Cup. They didn't won in any of their four friendly games they played in 2018 and that is quite concerning. Even if the matches against Austria, France and Brazil were quite difficult, in their most recent, vs Turkey, the showed gaps in defence and weaknesses. Perhaps, the most concerning thing for the Russian team, is the fact that they couldn't have the upper hand, even in a home game against an inferior team.

Saudi Arabia played much more friendly games than Russia, although they didn't have the best performance. In their most recent games they registered three defeats in a row, from Germany, Italy and Peru. The only good thing for Arabs is that before these games they managed to boost their moral with wins vs Greece and Algeria. The other one, is that even if they lose, they manage to score against very strong teams like Germany and Italy, where they were eventually defeated 2-1.

Russia and Saudi Arabia have never played before against each other and it's quite difficult to make predictions at the beggining of the World Cup. However, with the speciments that I have from the preparation games, I would dare a bet at Both Teams To Score @ 2.60 with a small stake (3 units).