No, you will need a senior sized blade to fit into a senior sized shaft. Putting in that junior sized blade would just fly right out. You will also need to determine what kind of senior shaft you have. There are two types, a standard fit and a tapered fit. Tapered blades will only fit in tapered shafts and standard blades will only fit in standard shafts. no compromising on that. usually a tapered shaft will be a .520 size or say tapered, a standard will have a larger opening and normally be measured at .620 size or be labeled standard. One you figure that out take a look at this page to find a suitable blade!