Lehmann coy on Watson's leg injury "He's got a little bit of a niggle ... but we'll let you": Australian coach Darren Lehmann on Shane Watson's injury. Cricket Australia refused to reveal the seriousness of Shane Watson's injury as concerns mounted about his fitness for the remainder of the Trent Bridge Test. Watson did not take part in Australia's running drills during the warm-up before the second day's play, instead walking lengths of the field with physiotherapist Alex Kountouris. Team management was evasive when asked for details about the injury or whether the all-rounder would be fit to bowl in the second innings. Ed Cowan had a forgettable first Ashes experience, suffering from a stomach bug and lasting just one ball in the first innings. The all-rounder pulled up sore after bowling four overs in the first innings and sustained what coach Darren Lehmann described as a niggle in his lower leg. He was hopeful of being able to bowl in the second innings but with his history of calf injuries - and just three days between the first Test and the second at Lord's - the injury does not inspire confidence in his ability to get through back-to-back Tests. "He's got a little bit of a niggle, but he's going to see Alex Kountouris and I presume he's going to bowl in the second innings, but we'll let you know," Lehmann said. Watson returned to the field on the opening day and opened the batting. He made 13 but didn't have to run much given 12 of them came in boundaries, before he and Ed Cowan fell to consecutive balls from Steven Finn. Michael Clarke stepped up to bat at No.4 despite his inferior record in that position, and was exposed to England's magician Jimmy Anderson at 2-22 when the ball was swinging under gloomy skies. Clarke averages 21 in 31 innings at No.4 compared with a commanding 63 in 98 outings at No.5. Clarke was bowled by a brilliant delivery from Anderson for a six-ball duck and Lehmann called on the top order to stand up and protect the captain and No.1 batsman. "That's the job of the top three isn't it, they've got to get through," he said. He wants to bat four and I support that. I like the captain batting at four. The openers have to bat longer than they did. Should Watson be unable to return to the bowling crease, more will be asked of first-day hero Peter Siddle, who inspired Australia to bundle out England for 215. Lehmann admitted Siddle's place was in doubt before the series, but in the end the Victorian was trusted to lead an attack made even more inexperienced by the promotion of teen debutant Asthon Agar. The young guys, it's the first day of an Ashes series and it's pretty big, so they probably got over-excited with the new ball more than anything else and they understand that," Lehmann said. Peter stood up when it counted and did really well - five for on the first day and led the attack as we expect him to do. Siddle conceded 27 in his first four overs but roared back into the contest to finish with 5-50, his 8th five-wicket haul in Tests. England paceman Stuart Broad was struck on the shoulder by an aggressive James Pattinson while batting but was expected to be fit to bowl on the second day at Trent Bridge.