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Pos. - Position (primary position first, plus any position played for 5+ games in 2017)
Level - Highest level reached over career. Post-season-only or brief call-ups from one minor league level to another excepted. Player on an inactive list for entire previous season will be listed on respective inactive list even if higher level previously reached.
   A+ denotes High-A (California, Carolina, and Florida St. leagues)
   A denotes Low-A (Midwest and South Atlantic leagues)
   A- denotes Short-Season-A (NY-Penn and Northwest leagues)
   YTD denotes player has yet to debut professionally
"40" Column
  ● denotes player is on Boston's 40-man Roster
  arb - denotes player will be eligible to file for pre-free agency arbitration in January 2018
  opt - denotes player has a player/team option for 2018
R5 - Eligible for December 14, 2017 Rule 5 Draft if not added to the 40-man roster on or before November 20, 2017
RL - Spent last season on Restricted List
NRI - ● denotes player is a non-roster invitee to spring training
NRI - denotes player has been re-assigned to minor league camp
PB - Piggyback
L = bats left (for hitters only); throws left (for pitchers only)
ƅ = switch hitter (for hitters only)

Free Agents
Major League Free Agents - Following the completion of the term of his contract, any player with 6+ years of major league service time who has not executed a contract for the next succeeding season shall be eligible to become a free agent. (Basic Agreement, Article XX(B)).
Article XX(D) Free Agents - Any player: (1) with 3+ years of major league service time and whose contract is assigned outright to a minor league club; or (2) whose contract is assigned outright to a minor league club for the second time or any subsequent time in his career may elect, in lieu of accepting such assignment, to become a free agent. (Basic Agreement, Article XX(D)).
Minor League Free Agents - On the fifth day following the completion of the World Series on the last year of a player's minor league contract, the player's contract shall expire and the player shall become a "minor league free agent" unless that player's club renews his contract.  (Major League Rule 55(a)).  Standard minor league player contracts are typically for seven seasons.