You have gotten good advice on how to do what you asked for, so I won't add to that.
But I would offer you a slightly different idea ---Your friend knows he charged the net and that is part of the dynamics of the game, I might opt for keeping the 'canvass size the same in all pix but allow his size in the frame to grow as he approaches. You can still alter his size in the frame a bit so he is never too small or too large, but his increasing size is part of adding the dynamics in the action you captured.
Just a suggestion for your consideration, do what you like.
Good Luck

Having just had another go to refresh my memory here's the quickest way to do it in PS. Not having lots of images of the same person to hand I just chose 3 images with a full height subject in different positions within the frame and different sizes. Object was to get them all the same height in the centre of a 2x3 vert crop.

a) Place your selected jpeg files (these will be uncropped, colour balanced PPd images) in a folder and for ease name them 1 to 8. (This is not essential)
b) In PS go to File/Scripts/Load Files Into Stack. Select the Files you want to use and select OK.
c) These files will then be loaded into PS as layers showing file names and on top of one another.
See Pic 1 for Info.

d) Select the lower layer by turning off the ones above it and place guide lines as your datum for getting the others to match.
See Pic 2 for Info.

e) Select both lower layer and one above it but reduce this one to 50% opacity. You can then move that layer around and resize as required to obtain good alignment. Repeat for each layer in turn.
See Pic 3 for Info.

f) When all layers are aligned place the crop tool box where you want to crop them.
See Pic 4 for info.

g) Ensure you return opacity of each layer to 100%. Select each layer in turn with all others off. Export each layer in turn to a known folder. They will all be the same pixel width and height and you can change this to whatever you require.

Pic 5 are the results side by side

Undertook something similar a while ago and from what I recall, all images were opened in PS (following any post work in ACR).

I then selected 1 image and dropped the others onto it one at a time and adjusted their position and scale to match. This is easily done by lowering opacity of each in turn, in addition I placed two guide lines horizontally to assist alignment.

The resulting layers on top of each other were then all cropped, retaining alignment, and then the pixel size of each cropped layer made equal.

The exercise was undertaken to produce equal sized subject and image files to place together to make this banner.