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This probably is the last thing the Caoitals should really do; but as long as Ovi is skating, the Caps will push..... and this does push the envelope.
I am sure Caps fans will say, we have Oshie and the kids, there is no need for Tarasenko. This maybe fair. But, in landing Tarasenko, the Caps do add a legit 2nd line RW. Further, this allows them to move Oshie to the 3rd line (he is really having a rough season) and move Mantha further down the line up (noting his streaky and inconsistent nature).
All in all, this really does give the Caps offense on all 4 lines - which could make them extremely dangerous when the dance begins.
I will concede that Edmonton would likely be an even better fit, but that is square pegs and round holes. It is double retention to make it work.
Conversely Washington has the cap space, and I suggest (currently at least) a clear role for Tank. It is easier and cleaner.