With a sublet property, the lease still binds the original tenant so they are still responsible for paying rent. However, the new tenant (or subtenant) is also a tenant under the Residential Tenancies Act. So with a sublet property, they are also responsible for paying rent when due.
The original tenant could choose to pay rent directly to the landlord, and collect the rent from the subtenant. Another option is to see if the landlord would agree to accept the rent directly from the subtenant. However, if the subtenant did not pay the rent for any reason, the original tenant would still be responsible for paying the rent.