The Rockies are insisting on a package of players that includes major-league talent and at least one prospect, Morosi adds.
Among the names Colorado has interest in is right-hander Dakota Hudson.
The Rockies are also expected to ask for at least one of St. Louis' top prospects: Dylan Carlson, Nolan Gorman, Matthew Liberatore, or Andrew Knizner.
Arenado is owed $234 million over the next seven years. He also owns a full no-trade clause and the option to opt out following the 2021 season. The Cardinals would likely ask Arenado to waive his opt-out as a condition of the trade, Morosi notes.
The addition of Arenado would give the Cardinals a formidable pair in the middle of the lineup alongside Paul Goldschmidt. Since his 2013 debut, Arenado leads all third basemen in homers (227), RBIs (734) and slugging percentage (.546).
He's also won seven consecutive Gold Gloves at the hot corner.
The Cardinals already employ Matt Carpenter, who has experience at third base. However, the 34-year-old veteran put together the worst season of his career at the plate in 2019, hitting .226/.334/.392 with 15 home runs and 46 RBIs in 129 games.