Cal Raleigh is a longshot to make his MLB debut on opening day, but it could happen. There are only two players ahead of him on the Mariners roster at the catcher position as Tom Murphy figures to be the opening day starter and Luis Torrens, who the Mariners acquired last year in the Austin Nola deal, figures to be his backup.
However, Murphy is coming off of a 2020 season that saw him get 0 action as he missed the entire season due to injury, if he were to struggle in spring training or get injured again, Raleigh could slide into one of the two roster spots for a catcher.
Another reason that Raleigh has a chance to debut on opening day is that he had a great Instructional League this fall. Instructional League was huge for some Mariners prospects this fall as none of them got to play in any real games against competition other than other Mariners since last march in Spring Traning, and Raleigh took advantage of the opportunity and was one of the Mariners best hitters.
As I said, Raleigh has a chance to make the opening day roster, but my guess is that he is called up sometime mid-season if Murphy or Torrens are struggling or get injured.