With Kucherov out for the foreseeable future, the Bolts currently have $9.6 million in cap space.
The Leafs did a similar strategy last season when they acquired Riley Nash from the Blue Jackets.
Toronto had the space to fit him under their cap, they then placed him on LTI after he was acquired, and then activated him for the start of the playoffs once he was cleared to play.
If Eichel returns for the playoffs, Tampa Bay can worry about next season's cap in the summer.