Dubai: Pakistan opening batsman Mohammad Hafeez on Sunday issued a warning to England batsmen: beware Saeed Ajmal's new mystery delivery in the upcoming Test series.Hafeez is well-placed to offer the advice â he has been facing the delivery that Ajmal has dubbed the teesra, meaning third in Urdu, in the nets for the past six months."Yes, I have played that delivery," Hafeez said. "It's a bit different and he has worked a lot on it."The first game of the three-Test series begins at the Dubai International Cricket Stadium on Tuesday when Ajmal has promised to reveal the delivery."It will be something new in international cricket," Hafeez said. "You will judge yourself when he bowls it. I can't reveal more about it now, it's his weapon."Ajmal took 50 wickets in eight Tests last year and often surprises batsmen with a doosra, a ball that drifts away from right-handed batsmen.Hafeez scored 647 runs in 10 Test matches last year during which Pakistan won three successive Test series â against Zimbabwe, Sri Lanka and Bangladesh. It drew the other two series against New Zealand and the West Indies.Hafeez had been playing Ajmal in domestic cricket for the last eight years and said the new mystery delivery is sure to surprise the batsmen."He has command on it because of his extra-ordinary work," Hafeez said of his teammate's new delivery. "I wish him success in this delivery."Every person has an ability to improve his skills and he has done that."Like Ajmal, Hafeez also bowls offspin and has provided Pakistan breakthroughs in Test matches. But, Hafeez has no secret weapon up his sleeve."I stick to my basics, what I was doing before," he said. "But if anyone has invented a new delivery then that will be good for the game."Pakistan have been forced to play their 'home' series abroad due to security concerns of foreign teams after gunmen attacked the Sri Lanka team bus in 2009. The attack in Lahore resulted in the deaths of six police officials and a van driver.