Replace outdated fan in Master, weird 4" recessed box beneath old fan. Do I need to replace the box and patch?

See pictures for more info. The previous fan had a large base that covered the entire square, the new fan does not. Not sure what the next step is here, any advise would be very helpful!

Pics: http://ift.tt/1PyU5YE New Fan: http://ift.tt/1MtYYrm

Submitted March 28, 2016 at 12:09AM by goppeldanger http://ift.tt/1pRZzJB