Neal, 34, had the final two years of his contract bought out by the Edmonton Oilers earlier this off-season. The 13-year veteran had five goals and 10 points in 29 games last season, but has scored at least 20 goals 10 different times in his career. In 850 career games Neal has 294 career goals and 555 points.
Frolik, 33, spent the past season with the Montreal Canadiens where he appeared in eight NHL games and two with the AHL's Laval Rocket. Over 13 seasons with the Panthers, Blackhawks, Jets, Flames, Sabres and Canadiens he has 159 career goals and 384 points.
Both players will be attempting to crack a Blues roster in need of depth scoring after the departure of Jaden Schwartz to Seattle and a potential trade of Vladimir Tarasenko.