"We recognize the extreme seriousness of this matter and will honor the confidentiality requirements of the League's program," the Colts said in a statement. "We nevertheless wish to assure Robert and our fans that he remains an honored and cherished member of the Colts family and that we support him as he deals with this difficult challenge."
Mathis, in a statement through his agency, said he and his wife faced fertility challenges and that he had sought medical assistance.
"I specifically asked the doctor if the medication he prescribed for me would present a problem for NFL drug testing, and unfortunately, he incorrectly told me that it would not. I made the mistake of not calling the NFL or NFLPA to double check before I took the medication at the end of last season. The union has worked very closely with me to present all of the facts and medical records for consideration of discipline that does not include a suspension because of the unique facts of my case, but the Commissioner refused the request."
Mathis, a five-time Pro Bowl selection, is coming off the best season of his career with 19½ sacks and 10 forced fumbles at the age of 32. Before 2013, Mathis had never accumulated more than 11½ sacks in a single season.
"I am deeply saddened that this situation will prevent me from contributing to my team for four games, and I regret that I didn't cross check what my doctor told me before I took the medication," Mathis said. "I hope that my fans will understand the unique circumstances involved here and continue to know that I am a man of integrity who would never intentionally circumvent the performance enhancing substance policy agreed to by the NFL and my union.
"The incredible blessing of this very upsetting situation is that, after I took the medication very briefly at the end of last season, we learned that my wife is expecting a baby. We are thrilled that we will be welcoming a new member in several months, but I apologize to my teammates, coaches and Colts fans that I will not be able to contribute to my team for the first four weeks of the 2014 season. I will work extremely hard during that time to stay in top football shape and will be prepared to contribute immediately upon my return."