If my memory serves me correctly, Aly @ 4 months old wasn't into balls, either. As a longer term exercise option, I wished for her to have some enthusiasm for fetching them. By about this time, I think I'd pretty much decided I wasn't going to return to hunting and Aly would exclusively become a companion pup. I wasn't worried my attempted methods of getting her interested in fetch may interfere of hunting training and activities.
By 4 months old, Aly loved her pink octopus Wubba (which is essentially a ball with tentacles). She began developing too great an interest in playing tug. Instead of just shutting down the tug game, I decided to use it as a reward for other learned activities.
The first thing she learned from playing tug was "release". If she wanted me to tug back a little or for me to torque her head a little, she'd first have to release it from her mouth, on demand.
When she became very reliable at releasing, the opportunity of a tug at Wubba became and alternative reward (as opposed to treats) for other obedience training... sit, stay, lay down, stand, look at my eyes, etc. The Wubba/tug thing also became my avenue of commanding Aly at a distance.
When at a distance, reward for success was initially a recall, so she could get a tug or two... then release was commanded. As a little time passed, reward was sometimes me throwing her Wubba to her... and then recalling her. Of course, she wanted that lil tug, so she always had Wubba in her mouth. Soon, me just tossing Wubba and her fetching it, with a release into my hand at the end, became part of the game.
I should have mentioned, Aly's 1/2 dozen favorite toys were given names. @4 months old, simply by saying a toy name, would prompt her to get it... because of course, that meant PLAY!
At around 4.5 to 5 months old, Aly's sharks vanished... almost overnight and began developing a real love of the actual training interaction. It was about this time I began directing her attention to the named "ball", which she still didn't have much interest in. Initially, reward was given simply for her going to the ball and touching it with her nose.
The next step was when getting her into a high intensity play/training mode... I would command Aly to "Get the Wubba!", 5 or 6 times in rabid succession. She'd get really amped at hearing "Get the..."! When it became the semi-frantic activity of fetching and not the object, I began intermixing "Get the Ball!"
Now, @ 19 months old, Aly is a ball fetching freak! If not involved in other activities, she would fetch a ball 25 hours a day. Be careful what you wish for!🤣😂🤣😂
Was this the correct or recommended method of shaping the pup's interest into an activity she didn't seem to have an interest in? I couldn't tell ya. Would Aly have naturally developed an interest in fetching balls? Maybe. None the less, we both had a blast!
Best of luck... and most of all, HAVE FUN!