If the subsequent runner has advanced and is standing on third base in a run-down between third base and home plate when the runner in the run-down is ruled out for offensive interference, the umpire shall send the runner standing on third base back to second base. If the subsequent runner attempts to advance toward home plate while the first runner is still being tagged out, this is called a balk. A balk does not score any runners nor award any bases, but it does result in a ball being put into play by the batter-runner who was forced to stop running. A batter cannot balk twice in an inning.
There are three ways that a runner can be declared out at any time during an actual play at bat: when he is not covering first base; when he is not covering third base; or if he is not covering home plate. If a runner is not covering any base when he is declared out, he must return to his original position. For example, if a runner is standing on first base when he is ruled out for interference, he must return to first base. If a runner is not covering third base when he is declared out, he must return to third base.
A runner is "on base" when there is no one out and he has reached any part of the field other than home plate.
7.03 Two runners may not occupy a base, however if two runners touch a base while the ball is alive, the subsequent runner is out when tagged. The runner who came before him is entitled to the base. 7.04 When no runner, other than the batter, is on the field, he or she may advance one base without being put out.
If a forced-to-advance runner is put out for the third out before a previous forced-to-advance runner crosses home plate, the run must score. Play. Two outs, bases loaded, batter walks, but runner from second gets overzealous and sprints past third base for home, where he is tagged out on a catcher's throw.
The ball will not be called live by the umpire until the runner has returned to the appropriate base. 8-2-3 After a following runner scores, a runner who misses a base while advancing may not return to touch it. Any runner who misses the first base to which he is moving and is subsequently called out is regarded to have advanced one base.
The runner from third base gets to home plate before the batter/runner gets to first base, yet the batter/runner is not the determining runner for the third out. Because the defense has focused their efforts on getting that runner out, the choice is made on the runner from second base.
A run is not scored if the runner advances to home base during a play in which the third out is made (1) by the batter-runner before he reaches first base; (2) by any runner being driven out; or (3) by a previous runner who is pronounced out for failing to touch one of the bases.
Because the outfielder has the option of throwing home or to third base based on the ball hit and the pace of the runners, the shortstop will line up at third base. If the runner takes too much of a turn around second base, the second baseman will be expecting the ball from a cut-off guy. In that case, he will field it and throw out the baserunner.
Shortstop is one of the most difficult positions to fill in baseball. While some players can handle the low workload required by this position, others need more time to develop their skills. There are several shortstops in Major League Baseball today who have never played third base before, showing how important it is for teams to learn you can't judge a player's ability at this position solely by how many games they play there. Although many shortstops do spend time at third during practice sessions or game situations, the true test of whether you can handle third base comes when you are making game-deciding errors there.
In conclusion, yes, the shortstop covers third base.