Sheffield United manager Danny Wilson admitted Portsmouth gave his side a stern test as they won 1-0 at Bramall Lane.
Nick Blackman struck from the spot in the 66th minute after Lubomir Michalik's reckless sliding tackle felled Chris Porter inside the area to give the hosts a victory which takes them level on points with League One leaders Tranmere.
Wilson said: "It was a very tough contest. They've got some very experienced players who made it difficult for us at times. They played some great football, I have to say.
"There were pockets of the game where we played some great football as well. I think you could see there were two promising teams who will be challenging at the end of the season.
"We've dug out a great result again. For the penalty, maybe the boy committed himself when he shouldn't have done. It was a great penalty again from Nick.
"It was end-to-end and I think you've got to applaud both teams for going out and trying win the game. The onus is on ourselves and we defended very stoutly again."