This question occurred to me when I saw center fielder Jon Jay of the Cardinals lose his glove off his hand while trying to catch a Ryan Vogelsong fly ball in the NLCS vs. the Giants: see the AP picture below, from this page.
If a fielder loses his glove while catching a ball, and the ball stays in the glove as the glove winds up on the ground or in the stands, sitting in the field of play or over the fence/railing, should it be an out or a hit (or foul ball)?
You could say that the fielder had to possess the ball in his glove in order to have it secured in his glove before it left his hand. Or you could say no, if the fielder had secured the ball, it would still be on his hand, not on the ground, so it’s no catch.
Here is what Rule 2.00 of the MLB rule book says:
A CATCH is the act of a fielder in getting secure possession in his hand or glove of a ball in flight and firmly holding it; providing he does not use his cap, protector, pocket or any other part of his uniform in getting possession. It is not a catch, however, if simultaneously or immediately following his contact with the ball, he collides with a player, or with a wall, or if he falls down, and as a result of such collision or falling, drops the ball. It is not a catch if a fielder touches a fly ball which then hits a member of the offensive team or an umpire and then is caught by another defensive player. In establishing the validity of the catch, the fielder shall hold the ball long enough to prove that he has complete control of the ball and that his release of the ball is voluntary and intentional. If the fielder has made the catch and drops the ball while in the act of making a throw following the catch, the ball shall be adjudged to have been caught.
Rule 2.00 (Catch) Comment: A catch is legal if the ball is finally held by any fielder, even
though juggled, or held by another fielder before it touches the ground. Runners may leave their bases the instant the first fielder touches the ball. A fielder may reach over a fence, railing, rope or other line of demarcation to make a catch. He may jump on top of a railing, or canvas that may be in foul ground.
No interference should be allowed when a fielder reaches over a fence, railing, rope or into a stand to catch a ball. He does so at his own risk.
If a fielder, attempting a catch at the edge of the dugout, is “held up” and kept from an
apparent fall by a player or players of either team and the catch is made, it shall be allowed.
Both “firmly holding it” and “finally held” indicate that the fielder does need to have the ball in his possession, that is, on his person, not just in his glove, in order for a catch and out to be made. I suppose this play has come up in an MLB game, although I’ve never heard of it happening. This is a little like the question of what happens when a ball hits a player and then goes out of play; that has been covered on this blog before.
Misc. Baseball 
In general, then, the glove is just an extension of the player’s hand. So if the glove is off his hand, it cannot count as a catch.
Makes sense to me.
Cheers, Bill
The answer is incomplete. Ball in glove…..glove with ball on ground…..glove is on ground but ball has not hit ground. When the outfielder picks it up he has control before the ball hits the ground. Catch?
This actually happened to me yesterday in an adult softball game.. There was a runner at first, and I was playing first base. The batter hit a hard low line drive to my backhand side. I caught it close to the ground backhanded, but then my glove came off my hand. The ball was sitting in my glove on the ground for a moment or two. The runner from first was running. I simply picked up the glove and ran to first to double off the runner. the umpires did say it was a double play (i.e., my catch was good and I had doubled the runner off of first). There was some minor disputing about this, but the call stood. I have never seen this type of play before at any level, but it seems to me it was a catch because the ball NEVER TOUCHED THE GROUND. This was clear not only to me as the person catching the ball, but to everyone watching closely, especially as I picked up my glove (with the ball in it) and not the ball itself to make the out at first. This is an interesting question!
Once your glove came off of your hand, it is NOT considered to be part of your hand, which would be needed for possession. So, the umpires got this wrong. Your glove being off of your hand and on the ground is simply a live ball; just as if it was sitting on the pitching rubber. Not a catch, shouldve been a live ball, and play continues. You couldve gotten a force out by throwing to 2nd base or stepping on 1st base, but ruling this a catch is totally wrong