The Tampa Bay Buccaneers defense was jolted Saturday when the NFL suspended cornerback Aqib Talib four games without pay for violating the league’s policy on performance-enhancing substances. The fifth-year pro said in a statement released by the team that he took an Adderall pill without a prescription ‘‘around the beginning of training camp.’’ He will not appeal the ban, which begins Sunday against Kansas City. Talib will also miss games against New Orleans, Minnesota, and Oakland, becoming eligible to return Nov. 5. It’s the second suspension of Talib’s career. He was suspended without pay for the 2010 regular-season opener and also fined one additional game check for violating the NFL’s personal-conduct policy. That discipline stemmed from an altercation with a St. Petersburg cab driver during training camp in August 2009.