Between respectable bulk, a series of significant resistances, and an impressive level of recovery via Harvest-fueled Sitrus Berries, Exeggutor can function as an impressive defensive tank. This vitality, when coupled with the recovery offered by Leech Seed, makes Exeggutor very difficult to KO, while simultaneously chipping away at the opponent. However, it is often difficult to initiate that Leech Seed cycle due to Exeggutor's lack of offensive presence, which is where Sleep Powder comes into play; by incapacitating a Pokemon for a minimum of one turn, Exeggutor is capable of safely setting up its Leech Seed, thereby improving its chances of stalling out the opponent. From this point, Exeggutor's primary objective becomes extending its own staying power, furthering its ability to chip away at Pokemon. For this purpose, Substitute is the option that offers the most tangible benefits to Exeggutor, protecting it from both status and powerful attacks while sapping away HP with Leech Seed. However, due to Exeggutor's low Speed, it is not always realistic to stall out by the merit of Substitute alone. Therefore, Protect makes a reasonable alternative, similarly allowing Exeggutor to stall out the opponent and providing the ability to scout moves in lieu of the ability to more effectively avoid status. Psyshock ensures that Exeggutor is not entirely reliant on Leech Seed to inflict damage upon the opponent; it allows Exeggutor to apply pressure to most Grass-types that are immune to Leech Seed, apply additional pressure to Pokemon with recovery moves, and prevent Qwilfish, the most notable Taunt user of the tier, from shutting it down and setting up entry hazards on it. Hidden Power Fire, though it sacrifices the consistency of a STAB move and the ability to combat Qwilfish, is capable of similarly pressuring Grass-types, while threatening some significant targets Psyshock misses out on, such as Durant, Escavalier, and Ferroseed.
The given EV spread, in tandem with a Bold nature, seeks to maximize Exeggutor's ability to tank and whittle away at physically based threats, with enough Speed to outpace minimally invested Lanturn, allowing it to either put Lanturn to sleep or set up a Substitute before compromising itself to status. A faster spread, specifically 248 HP / 16 Def / 244 Spe, can be used in order to get the jump on the vast majority of defensively inclined Pokemon and bulky attackers, though Exeggutor sacrifices a substantial amount of bulk in doing so. Due to the very precise nature of the set, it is very difficult, if not impossible, to make room for alternative move options to work with. However, it is technically possible to utilize Giga Drain over either Protect or Substitute, shifting Exeggutor's role from a stall-oriented tank to that of a defensive pivot, though it does face some serious competition from Tangrowth and Amoonguss in this role.
Exeggutor greatly benefits from Toxic Spikes, as the additional damage they can accrue alongside Leech Seed facilitates the stalling process immensely, though they can also be highly detrimental to it if they remain on its side of the field. Therefore, a Poison-type Toxic Spikes setter, such as Qwilfish or Drapion, is very helpful. Furthermore, supporting Exeggutor with a cleric, such as Clefable or Lickilicky, can further bolster it against the possibility of life-shortening status. In addition to status, Magic Guard users, such as Clefable and Sigilyph, give Exeggutor a great deal of grief, as they can't be stalled out through Leech Seed or status. A Pursuit user, such as Absol, Escavalier, or Spiritomb, does wonders for this dilemma, either isolating and KOing them or bringing them down to the point where Exeggutor can usually take them out with a Psyshock upon their next switch-in.