Cook, who succeeded John Sheridan at the Proact Stadium towards the end of last month, has had almost three weeks to assess the squad he inherited and feels the future of both players lies elsewhere.
"We're working hard on a daily basis to improve results and there will be changes in personnel," Cook told the club's website. "We can't just bring players in and put pressure on the club's wage bill, players must leave the club.
"Craig and Neal have both done well for this club but we feel that their futures lie elsewhere. The likelihood is that they'll both leave in the near future but, while they're here, we'll pay them the utmost respect."
Westcarr joined Chesterfield from Notts County in August 2011 and scored the second goal in the 2-0 win over Swindon in the Johnstone's Paint Trophy final at Wembley in March. The 27-year-old has scored three goals in 18 appearances this season.
Trotman, 25, arrived on loan from Rochdale 12 months ago before signing a permanent deal in January. He has made 15 appearances this campaign.
- Sports & Recreation