ANDERSON, Ind. -- As expected, the emotions were mixed as Indianapolis Colts linebacker Robert Mathis sat on the edge of his bathtub with his head down in his hands after getting the news of his four-game suspension for violating the NFL's policy on performance-enhancing drugs.

On one hand, Mathis and his wife, Brandi, were excited because they were going to be the parents to their third child, a daughter, Brielle Emma-Rose Mathis, who was born July 19.

Indianapolis Colts defensive end Robert Mathis isn't focused on the past, but is ready to get beyond his upcoming four-game suspension. Kirby Lee/USA TODAY Sports

On the other hand, Mathis let his team down because he took a substance, Clomid, that's banned by the league.

Mathis released a statement immediately after the suspension was announced May 16 that he took Clomid because he and his wife "faced fertility challenges."

But questions -- and rightfully so -- immediately started about whether Mathis took the banned substance for the strict purpose of helping to get his wife pregnant or if he took it to improve his on-the-field production.

"The timing was wrong," Mathis said. "I cost my team on the professional level. Personal level, I have a lifetime worth of smiles and kisses. I try to learn from it and move forward."

A simple Google search, phone call to a team official or somebody in the NFL Players Association could have avoided this problem for Mathis. He said in his statement in May that he "specifically asked the doctor if the medication he prescribed" was banned by the league.

"I didn't call the right person, ask the right person," Mathis said. "(I) didn't, so take your lumps and just rebound from it."

Mathis played with extra motivation in 2013 because there were doubts about whether he could still be an effective pass-rusher without linebacker Dwight Freeney lined up opposite of him on the other side of him. Mathis talked that about motivation, too, last season. He went from 8.0 sacks in 2012 to a league-high 19.5 sacks in 2013. So it's easy to understand why the question would come up about the Clomid.

Mathis didn't turn his cellphone off or shut his Twitter account down to avoid paying attention to the criticism. He kept his devices on so he could get through the negative comments to read the positive remarks from the "reassuring Indy fans." The criticism that ate at Mathis went away in the "atmosphere" after Brielle was born earlier this month.

"People don't see the position change," Mathis said. "The fact I'm now the No. 1 rusher in this game. People who know the game, the No. 1 rusher, it starts and stops through that guy. Of course there's going to be increased production moved to outside linebacker, but I'm not going to sit here until I'm blue in the face trying to explain because it is what is.

"I apologized for the professional side of it, the personal side of it. I have no regrets at all. I look at my baby's face in my phone every day and I have no regrets. ...I know how people are going to react, know what people are going to say coming off a season like last year. That's human nature."

Mathis, who is allowed to take part in training camp, is eligible to return to the Colts' active roster on Sept. 29. The suspension will cost him about $706,000, but the money is the last thing he's worried about when he's holding his baby girl, who already has him wrapped around his fingers.

"(Brielle) looks at me and sees no wrong," Mathis said. "She don't know how she got here, she doesn't care how she got here. She knows she's here and feed me. That's my job and that's going to be my job for the next 18 years or however long it takes, football will be long gone. She'll be here."