Can you exhaust Sun Disc during the sequence of playing a unit that discards, then playing Flame Chompers from discard, to give Flame Chompers ready instead of the first unit?

Ruling: No, you cannot exhaust Sun Disc in the middle of this sequence. The discard effect goes on the chain immediately after playing the unit, then the Flame Chompers effect immediately goes on a new chain, and Sun Disc doesn't have Reaction so there's no window to activate it between these events.

Sequence:

• Play unit with "if you play me, discard 1"
• Discard effect goes on chain immediately
• Flame Chompers ability goes on new chain immediately
• No window exists to exhaust Sun Disc between these steps

Nuances:

• Sun Disc must be exhausted before playing the unit if you want to give that unit (or the next unit played) ready
• The "next unit" that gets ready is determined at the time you exhaust Sun Disc, not during mid-resolution of other effects