A Mono Red Aggro goes with winning fast in the early turns, maintaining an optimized opening, and gaining card advantage with every spell cast. This strategy is a challenge to keep up with if going with sideboarded games.

Sideboarding in Pioneer for a Mono Red Aggro deck typically involves adapting your strategy to better counter your opponent’s deck and addressing potential weaknesses in your deck.

Here’s a sample sideboard for a Mono Red Aggro deck in Pioneer. Do take note that possible adjustments are to be made once a new set is released:

1. Roiling Vortex: This card is effective against control decks and opponents who rely on life gain. It can prevent your opponent from gaining life and punish them for casting non-creature spells.
2. Smash to Smithereens: Use this against artifact-heavy decks or opponents who rely on key artifacts. It can deal damage to your opponent while also removing problematic artifacts. Abrade is also another versatile removal that can target both creatures and artifacts.
3. Searing Blood: Bring this in against creature-heavy decks where you want additional removal. It deals damage to a creature and its controller if the creature dies this turn.
4. Tormod’s Crypt: Helpful against graveyard-based strategies. It can exile your opponent’s graveyard to prevent them from recurring creatures or spells.
5. Obliterating Bolt: Good for dealing with larger creatures or a relevant planeswalker. It can then exile them if they die, ensuring it won’t come back.
6. Rampaging Ferocidon: Effective against decks that rely on life gain or tokens. It prevents your opponents from gaining life and punishes token strategies.
7. Scorching Dragonfire: Another option for creature removal. It can exile small creatures and is particularly useful against recursive threats.
8. Shrine of Burning Rage: Against control or grindy matchups, this card can slowly accumulate counters and become a win condition.
9. Rending Volley – An uncounterable spot removal aligned to deal with White or Blue creatures, it is usually in three to four copies to be relevant against the Spirits or Mono-White aggro matchups.
10. Aethersphere Harvester: Bring this in against aggressive decks or matchups where you need additional lifegain and flying threats.

Remember that your sideboard should be tailored to the specific metagame you expect to face, so adjust your choices based on the local Pioneer tournament environment or your knowledge of common opponents.

Sideboarding is an essential skill in Magic, and adapting to your opponent’s strategy can significantly improve your chances of winning matches.