Not just watching, but feeling. And then something happens. It may be a draw offer, which the player can refer to his captain, not for advice about the game but rather about the match position. Or occasionally an incident - probably in time trouble, when points may be sprayed like confetti. Did the player's flag fall before he reached the time control - in which case he has lost? Or was the clock faulty? Did he touch the piece, in which case he has to move it, or did his hand merely hover?
After hours of steadily rising and essentially impotent anxiety, the captain may suddenly be thrust into the fray, but he must somehow remain calm.
I'm currently at the Spanish Team Championships in Salamanca where there has been just one serious incident, albeit not in real time. In the first round Endesa, from Ponferrada near Len, fielded their top four, including the Georgian grandmaster Gio Giorgadze on board one.
Unfortunately Giorgadze, as they must have known, hadn't made it to Salamanca, so they defaulted the top board and were automatically awarded a half-point penalty.
Three rounds later Endesa played Olivar (Saragossa). Quite deliberately they again fielded a team with the absent Giorgadze on one. Olivar immediately protested, claiming the match 4-0 on default, for not only were they now all facing stronger opponents, but in shifting boards Endesa had nullified all their preparation. But Endesa subsequently racked up three wins for what they hoped would (including the penalty) be a 21/2-1 victory! This time the result was allowed to stand; but they were warned to play all boards in future.
Here, briefly, is a win by Endesa's top board from an earlier round:
White: Alfonso Romero Holmes
Black: Miguel Illescas
Black to play
17...e5?! 18 fxe5 Ngxe5 19 Be2 Kh8 20 Qc3! Ra5 21 Nh5! Nxd4? 22 Bxd4 Bxd4 23 Rxd4 Rc5 24 Rf4!! 1-0
17...e5 looked good but 17... Nxd4 18 Bxd4 Bxd4 19 Qxd4 Qxd4 20 Rxd4 Ne3 was safer. 19... Kh8 avoided the d pawn going with check in some lines; but the cure turned out to be worse than the disease. In the final position Black is busted, since if 24... Rxc3 25 Rxf8 mate or 24... Rxf4 25 Qxe5.