Steve Smith admits he did not know if he "still had it" after making a sensational return to Test cricket with Australia in the Ashes.

The former captain made a sublime century in Australia's second innings on day four, his second hundred of the match, scoring 142 as Australia declared on 487-7 to set England a daunting target of 398.

It has been a remarkable comeback to the Test arena for Smith after he was banned for his part in the ball-tampering scandal that rocked cricket.

An elbow injury earlier this year also played on the mind of Smith, who reflected on an emotional few days at Edgbaston. 

"It's been incredibly special, obviously I've been out of the game for a while. I was a little bit nervous coming into the first day and I don't normally get nervous coming into games," he told Sky Sports.

"It was nice to get that first hundred, I've never scored hundreds in both innings before, so I was keen to do that.

"It was a very emotional first hundred on day one, I was kind of lost for words and had to take a deep breath, my spine was tingling.

"There was a time I didn't know if I wanted to do it again, just before I had my elbow brace off, I didn't know if I had it in me. 

"I've never felt that way about cricket in my life. It was strange feelings and emotions, now I'm back doing what I'm enjoying, practising hard. Wearing this cap, it's an honour and I'm grateful."

On the feeling of making his first hundred, Smith said: "It did overcome me, I had to take a few deep breaths. 

"It's really special, it's great to be back playing Test cricket, I love Test cricket, I love playing England, it feels like Christmas morning every morning coming here and doing this."

Smith's heroics and a fine century from Matthew Wade, his first in Test cricket since January 2013, completely altered the state of the game with England now needing a huge effort to secure a draw.

The ex-skipper pinpointed spinner Nathan Lyon as the key for Australia on day five.

"I was able to have some good partnerships with Travis Head, who I thought played really well, and Matthew Wade played with such freedom – I'm really proud of him and the way he played," he said.

"There's going to be some spin, Nathan Lyon's obviously going to be important for us.

"There's a bit of variable bounce, [we need] the quicks hitting the stumps and Gazza doing his thing from one end, quicks rotated from the other."