Ashes 2015: Brilliant Steven Finn back from rock bottom - Agnew

Steven Finn's five-wicket haul was his first in a home Test since June 2010

Steven Finn's renaissance is wonderful news for the bowler and wonderful news for England, especially given the injury concern over James Anderson at such at crucial stage of the Ashes.

By the time Anderson left the field to undergo treatment on a side injury that must make him a doubt for the fourth Test at Trent Bridge, Finn's brilliance had taken England to the verge of a series lead as they reduced Australia to 168-7 by the close of day two.

I have huge admiration for Finn, who has been to rock bottom and got back to the top.

I have a really sad memory of him on the last day of the final Ashes Test match in Sydney in January 2014 when England lost in three days.

Finn, who had not been picked for any of the Tests, was bowling at cones in the nets for the umpteenth day in a row looking utterly downtrodden.

There he was, sending down ball after ball at about the pace I used to bowl. He had lost everything: his pace, his rhythm, his enthusiasm, and it was a horrible sight. I thought to myself 'This guy needs putting out of his misery'.

When Finn was eventually sent home during the one-day series, then-coach Ashley Giles described the 26-year-old as "unselectable". It was an unfortunate term but it was entirely accurate because sending Finn home was the kindest thing to do.

Former England bowler Angus Fraser has played a huge role in Steven Finn's rehabilitation, says Agnew

It has taken time, but Finn's bowling has been dismantled and put together.

Great credit must go to his bowling hero and mentor Angus Fraser, as well as the other coaches at Middlesex, who have helped him finally rediscover that great knack for taking wickets that was so in evidence during the first two days at Edgbaston.

As a bowler, when you truly find your rhythm the game becomes effortless.

Finn has bowled a lovely line, has been hitting the crease at a good pace and finding that nasty bounce which makes him so dangerous.

Some of his dismissals are unusual - look at the way Steve Smith and Mitchell Johnson's mis-hit pull shots sent the ball ballooning into the air - but Finn is very tall and when he bowls the short ball batsmen often underestimate how high it's going to bounce.

They play a bit low, the ball hits the top part of the bat and up it goes.

Finn is also as nice a bloke as you will find in the game. Players have been queuing up on Twitter to express their delight for him after his five-wicket haul because he's such a warm and generous guy.

James Anderson will be assessed for a "tight side", according to England's management

England will need Finn to perform just as well at Trent Bridge as he has at Edgbaston because if Anderson has anything more than just a slight strain he will not be able to play in the fourth Test.

Side injuries can be a big problem for a bowler and unless you allow them to fully recover they can easily go again.

England's medical staff will do all they can, but Anderson would have to be bowling flat out on Wednesday at the latest to have any chance of being passed fit to play on Thursday.

With or without their bowling talisman, England appear certain now to be heading to Nottingham next week with a 2-1 lead after another dreadful batting display by Australia.

The pitch has done just enough to be interesting but it's not a minefield and some of their ineptitude has been extraordinary.

With England back in the ascendancy, Michael Clarke's side have serious work to do in order to get their Ashes campaign back on track.

Jonathan Agnew was speaking to BBC Sport's Sam Sheringham.