The seven-letter answer is:
GORILLA!
Why? Firstly:
Count up the number of times each numbered player receives the ball to get the following 29-number sequence:
66, 117, 116, 32, 100, 105, 100, 32, 121, 111, 117, 32, 115, 101, 101, 32, 116, 104, 101, 32, 95, 95, 95, 95, 95, 95, 95, 32, 63.
Note that if you rely on the CSV file rather than counting the passes in the GIF (which would take a very long time!) you need to discount the initial occurrence of '1', as this is the player just being in possession of the ball, not the result of a completed pass - thus there are 67 1's in the file, but only 66 of these are completed passes.
Next, notice:
That the number 32 crops up a disproportionate amount of times here. Since the number 32 is the ASCII encoding for a space, this suggests we should convert each number into its ASCII equivalent. This yields (ordering the players numerically from 1 to 29 by their shirt numbers):
But did you see the _______ ?
To replace the underscores with a seven-letter word, note that:
This puzzle is an adaptation of a very famous 'selective attention' test by Daniel Simons and Christopher Chabris, which @F1Krazy inadvertently linked to in the comments! In this, a group of white-vested players and a group of black-vested players pass a basketball between each other and the viewer is asked to count the number of passes by white-vested players. The catch is that at the end of the exercise the assessors reveal that while the viewer was so focused on counting the passes, somebody dressed in a gorilla suit walked right through the middle of the players, turned to face the camera and beat their chest before walking off again - and a large number of people do not notice this while their attention is focused on the counting!
For this reason, I believe the final sentence the OP is looking for is:
But did you see the GORILLA ?
Post-script: I also note the OP's choice of name for the character in this puzzle:
In the US sitcom Friends, Ross has a pet capuchin monkey called 'Marcel'! Clearly a pop-fiction nod from the OP there to an ape/monkey connection :)