Yes, I’d say tension is a major part of it. It is my assertion that there is no pressure situation in any sport nearly equal to that of being down by a run in the bottom of the ninth inning with two outs and a man on base. There’s nothing like it in any sport except baseball, in my opinion.
Why? Because in baseball, if you excuse my waxing poetical here, one out is all you need. With only one out, you can play forever. You can score fifteen runs on a single out; or you can whiff on three straight and go down swinging. Down by three touchdowns with 0:16 on the clock? Forget it. The game’s over. Down by four goals with 0:25 left in the third period? Not close. Down by 26 points with 0:20 on the shot clock? Don’t bother.
But in baseball, you can do it. You can beat the devil, you can live forever, you can stretch out the summer by just one more game.
If you know anything about baseball, then you know the players are not surprised by what’s happening on the field. The fans aren’t surprised. They know what’s coming. So there’s a man on first and second, one out, right-handed hitter at the plate and a lefty changeup artist on the mound, not much of a heater but he’s got a wicked curve. The fans are waiting for the double play ball, a sharp grounder to short. The batter knows he’s going to see something off-speed, probably low, probably low and inside, and he’s going to do his damndest to punch that ball the other way into right field. The pitcher knows he’s got to induce the batter to swing over and early so the ball trickles to the left side. The shortstop is on his toes: the next ball belongs to him. The first baseman wants to close up the gap on the right side to take away the opposite-field single, but stay close enough to the bag for the 6-4-3 double play ball. The catcher is ready to block the ball if it goes in the dirt, as a wayward curveball can do. Everybody on the field knows what’s coming, what could be coming.
The tension for the fans lies in the question: will it happen like that? Will the batter ground out to short into a double-play? Will the runner from first break up the play and throw his spikes at the second baseman as he slides into the bag, out by a mile? Will the throw to first be on-line? Or will the batter single sharply to right, challenging the right fielder with a cannon for an arm, daring him to throw out the second-base runner as he rounds third headed for home? Isn’t the second baseman playing too far over? Why does the pitcher keep shaking off that sign, we know what he’s going to throw? If they score this run, will they pull the pitcher? How much gas has he got left?
Anyway. I love baseball. I can’t stand the tension: it’s a delirious agony to watch, a splendid ordered chaos. But maybe that’s just me. 
FISH