Two-time Grand Slam champion Andy Murray launched a playful dig at Andy Roddick on Twitter after he spotted the former world number one tennis star out jogging.

Murray is preparing for tomorrow's Wimbledon semi-final against Roger Federer, while retired Roddick has been in London commentating on the action for the BBC.

Before Thursday's practice session, Murray spotted the American keeping his fitness levels up and the Scotsman opted to poke fun on social media.

The 28-year-old tweeted: "saw andyroddick running through wimbledon common on my way to practice this morning..Wasn't the pace I expected from an ex world no1."

In response, Roddick wrote: "Screw the pace I was running. I'm just excited that someone can vouch for me having done any exercise at all! #nailedit"

Roddick, who retired in 2012, reached three Wimbledon finals in his career but failed to win any of them.