They're gaining like 1.5 million? Ceci is going to demand 5M.
Ceci has arbitration rights. It'll go to arbitration and if he wins more than $4.4m then Toronto can walk away making Ceci a free agent.
For now, he has no contract against the cap, while the Leafs shed $6,6m in Zaitsev & Brown. They already have $5.5m in cap space and an LTIR contract in Horton ($5.3m).
At minimum they have their original $5.5m space, plus the additional $6.6m they're picking up in the trade. And, they can add a player to fill Horton's spot. $12.1m plus the $5.3m of LTIR.
They have about $15m-$16m. If Marner signs for $11m that still leaves them $4m-$5m to sign some D. Rumours are they want to bring back Hainsey.
Of course, if Ceci gets a $4.35m award in arbitration, they're screwed again if they go ahead and sign Marner & Hainsey and can't walk away from Ceci.