Here's another source. From J/R, chap. 2, section F:

"It is a play if there is a
(1) tag or tag try of a runner
(2) tag or tag try of a base
(3) throw to another fielder in a try to put out a runner
(4) rundown, or
(5) balk."

Notice that every action included as a "play" involves a throw, a tag, or tag try, with the (technical) exception of a balk. Fielding or catching a batted ball does not involve a throw, a tag, or a tag try, and is thus not a play for the purpose of the relevant rules.

Here's another way to think of it: a play under this definition always presupposes possession of the ball. You can't tag a runner or balk or throw the ball unless you have the ball. But fielding or catching the ball presupposes NOT possessing the ball, and thus cannot be a play in the relevant sense.

I still think it's bizarre that you can have an out without a play, but that looks solid to me.

Is is possible that you're using the wrong meaning of the word "play" for the purpose of this this interpretation?

I think somebody else stated that "hey nice play" is not the same "play" that we're discussing.

No, I've got that. I just think that an out-producing action by a fielder would have been a play since it produced an out. Not all plays produces outs and, apparently, not all outs are produced by plays. (Although the more I think about this it occurs to me that strike outs also aren't the result of plays.)

The thing I'm going to take away here is that plays can only start with a player already in possession of the ball.

J/R also says what's not a play:

It is not a play if there is only

(1) an appeal (although a play can occur during an attempt to appeal)
(2) a fake or feint of a throw, or an interruption of a throw,
(3) a step or several steps toward a base or runner that do not result in an actual tag attempt,
(4) a dropped line drive or pop fly.

No mention in either section of what is a play or what is not a play about a caught line drive or pop fly.

So I think you have to read the base award case plays since that's what's going to determine what is or is not a play. Would that be right...when it's not in the rules, we have to go do authoritative opinion on how certain plays are interpreted.

I definitely understand the logic, and again I want to stress that I'm not just being argumentative for argument's sake. However, while the rulebook is often messy, it's usually good at using words like only, always, etc when that's what they meant. Ditto J/R and MLBUM. All of these are plays. I wish this quote said "It is only a play if...". As standing, it says these are plays, but doesn't definitively tell us these are the ONLY plays. OTOH - one point in this statement's favor is that other than the question at hand, I can think of no other "plays" that are not listed here - indicating that this MAY have been an attempt to list them all, despite missing the word "only".

Yes, except the case plays seem to cover anything you could think of EXCEPT a catch. None answers the simple question of "Is a catch a play". Before this thread was born, I have always assumed "of course it is".

Which is probably why it's not covered.

From MLBUM:

5.6 Awarding bases on wild throws

In making such awards, keep the following points in mind:

1. If the throw is the first play by an infielder and the batter-runner has not reached first base when the throw was made, award all runners from time of pitch

2. If the throw is the first play by an infielder and all runners including the batter-runner have advanced a base when the throw was made, award all runners from their position at the time of the throw

3. If the throw is not the first play by an infielder or the throw is made by an outfielder, award all runners from their position at the time of the throw

My thoughts:

Interps 1 and 2 deal with the first play by an infielder and uses the word "throw" as being the first play. It does not mention catch or fielding an in-play batted ball. We have to assume that a catch or fielding a ball can't be the first play because the base award interps all use the word "throw" and the runner and B/R's position at the time of the throw or the time of pitch

From MLBUM:
The approved ruling of OBR 7.05g provides that when the first throw is by an infielder after runners AND batter have advanced one base, then runners are awarded to bases from their position when the throw was made. (See item 2 above) This can happen on a high fly ball that an infielder goes back to catch but drops, during the time the batter and runners have clearly advanced one bas; then, in attempt to put out the batter-runner, who has already passed first base, the fielder throws the ball into the stands. While it is the first throw by an infielder, the runners, including the batter-runner, had advanced one base before the throw and accordingly are awarded two bases from the base they last touched when the throw was made. Before awarding two bases from the base last touched by the runners, the umpire must judge that all runners -including the batter-runner - have definitely advanced to the next base before the throw was made.

My thoughts:

In the above example of the dropped fly ball by an infielder, this would have to occur with two outs, because with <2 outs R1 would be retreating back to 1B with less than 2 outs and it would not be likely that both R1 and BR would reach their next base on the dropped fly ball by an infielder. Likely, R1 would be forced out at 2B. With two outs, both R1 and B/R would be "running it out" and would be able to reach the next base without a problem. Then we'd have a TOT award instead of a TOP award.

If I recall correctly, your example involves a runner who is stealing on the play with < 2 outs. The ball is caught and in an attempt to double the runner off of 1B, the ball is thrown into DBT. The award based on the MLBUM interp is two bases from the time of pitch because the throw was the first play by an infielder. (it said nothing about the catch)...we have a couple of inferences to make regarding the above example, but it seems pretty clear to me on the appropriate base award.

Did I clear anything up? I'm going to post this now, then go back and read the OP again...because I've typed too much to lose all of this. My apologies if I missed anything of relevance in the OP

It doesn't necessarily follow from just what you posted that a catch isn't a play.

"If the throw is the first play" doesn't mean that only throws are plays. For example, if F4 tries to tag R1 and then wings it into the first base stands, the throw is the second play. It could be possible that a catch would be like a tag.

We still haven't found explicit proof one way or the other. It's not listed as a play but it's not listed as not a play either.

Okay, here's some more from MLBUM regarding a play or attempted play:

5.1 Play or attempted play

The following interpretation of "play or attempted play" applies to both awarding of bases and appeal plays 7.05g and 7.10 respectively.

A play or attempted play is interpreted as a legitimate effort by a defensive player who has possession of the ball to actually retire a runner. This may include an actual attempt to tag a runner, a fielder running toward a base with the ball in an attempt to force or tag the runner, or actually throwing to another defensive player in an attempt to retire a runner. (The fact that the runner is not out is not relevant) A fake or feint to throw shall not be deemed a play or an attempted play.

Example:

4. Runners on first and third, runner on first stealing as ground ball is hit to shortstop. The shortstop feints a throw home but does not throw-instead throw to first and into the stands; during this time the runner from first has rounded second base.

Ruling: The feint by the shortstop toward home is not considered a play or attempted play; thus the throw beyond first is the first play by an infielder and awards should be made from the time of the pitch.

Okay, here's one that might help as well...it doesn't exactly match the OP, but we might be able to fit a square peg into a round hole.

From MLBUM:

(13) The following play occurred in a Major League game and leads to a number of questions regarding appeal plays. The rulings below provide insight into various regulations concerning appeals and awards.

Play: R1, no outs, hit-and-run. Batter hits a line drive which strikes the pitcher in the back, flies into the air, and it caught in flight by F5 for an out. The runner on first is nearly to 2B when the ball is caught. The third baseman throws to first, attempting to double the runner off first base; however, his throw is wild and goes into DBT. At the time of the throw, the runner had not quite reached 2b. When the ball goes out of play, the runner from first has rounded second base (touching second as he rounded it) and is several steps towards shortstop.

a. What is the proper award?
Ruling: Third base-two bases from the time of the pitch because this is the first play by an infielder My words: (notice the first play was not the catch)

b. What if the runner is beyond 2b at the time of the throw? Is the award then home?
Ruling: No, the award is still third because the throw was the first play by an infielder. NOTE: See Section 5.11 for situations when a runner is initially awarded two bases from his position at the time of the throw, after which he is subsequently awarded two bases from his original base

This is perhaps the strongest thing we've seen. Two aspects to examine here as I see them is

1) What is the difference between a batter-runner and a runner?
2) What is the timing on possession of a catch related to the effort of the fielder in retiring the batter-runner by catching the ball?

On 1 I don't think there's a material difference for the purpose of this rule. If F2 fields a bunt and tries to tag the BR and then wings the ball into the stands trying to retire R2 at third I think the throw would be the second play. So a catch would be a legitimate effort to actually retire a runner.

What you don't have is possession of the ball until the end of the effort. This is still somewhat lacking as you do end up with a player having possession having made a legitimate effort to retire the runner.

So the key question from this is do you have to have possession at the start of the effort to have a play?

I think that's implied here, but it's not explicit.

I think this one seals it.