Which Red Sox player is most responsible for sending Boston to the World Series?

Each October, the MLB postseason belongs to someone or something. With so much good baseball packed into one month, it's sometimes tough to follow all the madness. So, we created the Baseball October Arbitrary Ranking Device (The B.O.A.R.D.) to keep track of it all.
With their 4-1 win over the Astros last night, the Red Sox ensured that this year's Fall Classic will begin at Fenway Park on Tuesday evening. 
In a series that saw two evenly-matched teams go blow-for-blow, the biggest separator for the Red Sox wasn't AL Cy Young candidate Chris Sale or triple crown contender J.D. Martinez or AL MVP favorite Mookie Betts. Sure, those dudes were all good and delivered in some big spots for the Sox, but they weren't No. 1.
Who was? Watch the video at the top of this post to find out!