If I play a spell that costs 4 energy and my opponent counters it with Deft or Not So Fast, can I still banish the card and proc Jhin's legend ability?

No, you cannot banish the spell with Virtuoso's ability if it has been countered.

According to Rule 425.1.b and RiftJudge FAQ #9779 (and FAQ #10308), a spell that is countered is not considered to have been "played." Because Virtuoso's ability triggers only when you "play a spell," a countered spell fails to meet the required condition for the ability to trigger.

Furthermore, per Rule 425.1.a, a countered spell is immediately cleared from the chain. Since the spell is no longer on the chain, it cannot be targeted or banished by Virtuoso’s effect even if the trigger condition were met.

Summary of the Sequence

1. Playing the Spell: You play a spell and pay its costs. It is placed on the chain as a Finalized Chain Item.
2. Reaction: Your opponent plays a card (like Defy or Not So Fast) to counter your spell.
3. Resolution: The counter resolves, and your spell is cleared from the chain.
4. Trigger Check: Because the spell was countered, it is not considered to have been "played" for the purpose of triggering "When you play a spell" effects. Consequently, Virtuoso's ability does not trigger.

Note: While you cannot banish the spell or trigger the legend ability because the spell was not "played," please note that per Rules FAQ Clarification 2026-04-29, if you were attempting to use the spell cost to satisfy a separate alternative cost for Jhin, Meticulous Killer, the energy you spent remains considered "spent" even if the spell is countered.