This is a man who claims he is no longer fit enough to play competitive football yet aims to cover more than 26 miles in under four hours.
“It’s a different kind of fitness,’’ he said. “Since I had my back operation, my right glute muscle doesn’t fire, so I no longer have that speed or power to play at a decent level.
“But if you’re plodding in a marathon, then I will be able to plod all day.’’
Plodding? The Welshman is surely doing himself and those thousands of runners preparing for the marathon a massive injustice.
But for a sportsman like Speed, taking up long-distance running was a natural sequel to a distinguished career which saw him win the title as a youngster at Leeds, play for boyhood heroes Everton, experience Champions League football with the Toon and an Indian summer at Bolton before arriving at Bramall Lane two years ago.
Raising money for the Sir Bobby Robson Foundation and also the Everyman charity set up by his ex-Wales team-mate John Hartson has kept him going as he pounds the streets in readiness for the big day.
“Stamina was always one of my strengths,’’ said Speed. “In my final season at Newcastle I played 61 games and I remember in my last-ever game for them, my Pro-Zone stats were right up there.
“That was one of the reasons Sam Allardyce signed me for Bolton.
“Mind you, running 26 miles is as much about being mentally strong as anything else.”
Speed decided to run a marathon last summer and chose Sir Bobby’s charity after attending the former England manager’s emotion-drenched memorial service at Durham Cathedral. “Bobby did a lot for me,’’ he added. “Sometimes without me even realising it.
“Newcastle was probably the happiest time of my career, even though we didn’t win anything.
“When Bobby was manager, it was fun, but, more significantly, I played my best football for him despite already being in my 30s.
“He created a wonderful environment and that Champions League campaign we enjoyed was just a fantastic time.
“No-one ever has a bad word to say about Bobby and attending that service for him just struck a chord with me.
“When I finished playing, I didn’t want to get fat. I’m someone who enjoys his food and likes a drink now and then.
“There’s no getting away from the fact that if you train every day you’ll stay slim, so when I realised I wouldn’t be playing again, I set my sights on running a marathon.’’
I don’t think I’m anything special. For me, the hardest part is finding the time to put the hours in.’’
Speed is currently running 14 to 16-mile sessions, usually on Saturday mornings before games when he has Blades’ fitness coach Dean Riddle for company.
“I struggle with the pace because when I’m on my own I go far too fast and, by the end, whatever distance it is, I’m on my knees,’’ he said.
“The other day I did a 14-mile run 11 minutes quicker than I would have running with Dean, which is ridiculous really. I couldn’t have kept that up for 26 miles.”
Speed is working towards twin targets – helping steer Sheffield United into the play-offs and crossing that finishing line on The Mall.
He added: “Nothing can ever replicate the feeling of scoring a goal, not even completing my first marathon. But if I can achieve both those targets, I will feel very satisfied.”
ANYONE wishing to donate to the Sir Bobby Robson Foundation by sponsoring Gary Speed in the London Marathon should log on to http://www.justgiving.com/GarySpeed11