With leaders West Ham thrashed 5-1 at Ipswich the Saints could have gone level on points but had to settle for a point after being held by the Bluebirds.
Southampton needed a second half penalty by Rickie Lambert - his 19th goal of the season - to cancel out Craig Conway's 36th-minute opener for Cardiff.
Haywood's penalty award for Southampton, 11 minutes into the second half, was a case of third time lucky.
"I've watched the video and we had two stonewall penalties turned down before that," claimed Adkins.
"There was no question Lambert was manhandled in the box in the first 10n minutes and early in the second half we ought to have got another when Adam Lallana was fouled on the byline.
"That said, it was a good point and I thought we played some good football in the second half and created some good chances.
"We could have won, but with West Ham being beaten so heavily, there's still plenty for us - and Cardiff - to play for."
Cardiff manager Malky Mackay was delighted with a draw.
"We locked horns with a side that has led the Championship for much of the season and came away with a creditable result," he said.
"We created as many chances as they did and could have won it.
"It was an entertaining game in which we shaped up well, particularly defensively, where I thought we were very sound.
"I was particularly pleased with Stephen McPhail, playing in front of the back four," he said.