Australia's nemesis from the 2013 Ashes has found form in the latest worrying sign for Michael Clarke's men.
Ian Bell admitted his place in England XI was in serious jeopardy after a barren run of form in the past four Tests.
Bell scored one in the first innings of the Ashes opener, but delivered a composed 60 in the second dig as England recovered from 3-73 to reach 289 in Cardiff.
"It's been a testing period for me," Bell said.
"There's no doubt I've been concerned.
"You have to dig deep sometimes, have to look right inside and work really hard."
Bell scored 562 runs in the 2013 Ashes, earning him the Compton-Miller medal awarded to the player of the series.
Since then, England have undergone a significant transformation, dropping all five Tests in the 2013-14 Ashes along the way.
Bell suggested new coach Trevor Bayliss, who started 12 days before the first Test got underway at Sophia Gardens, had already made a big difference.
Bell added that the aggression and enthusiasm of young guns Joe Root, Ben Stokes, Jos Buttler and Moeen Ali was infectious.
"It's a different way of seeing the game, these guys just want to go out and take every option on," he said.
"It's a very good environment at the minute. It's about being positive all the time, which is completely different to when I started."