Yoast tells you what people search for, i guess noone searches for "Dog of the week".
If you write for a targeted Keyword, you should do that only one time - otherwise, what should google show in SERPs??
But in your case, Dog of the week is not the targeted keyword. Don't know how people searching for dogs you write about, but that should be the target keyword - maybe for the category - and with the post about the dog of the week should target other things. Maybe "brown labrador retriever puppy"
]
But tell that a client..