The Expos had a strong tradition of squandering talent and then trading it away right before it got great.
Larry Walker
Pedro Martinez
Randy Johnson
Vladimir Guerrero
Rondell White
Moises Alou
Andres Galaraga
Cliff Floyd
Carl Pavano
Kirk Rueter
Marquis Grissom
Delino DeShields
Andre Dawson
Most guys on that list became good/great while playing for the Expos.
Pedro won a Cy Young as an Expo, Guerrero cemented his HOF career in Montreal, Dawson same, Grissom's best years were in Montreal, Walker and Alou were All-Stars in Montreal, Carl Pavano and Rueter... not even sure why they made this list, DeShields best years were as an Expo, Galarraga was a star with the Expos, Rondell and Cliff Floyd are examples of how great the Expos farm system was they both were All Stars as Expos.
The only guy on that list that left Montreal and *then* became great was Randy Johnson who was sent to the Mariners in a trade involving Mark Langston. It even took him a few years in Seattle to work out his control issues but then the rest of course is history.