Australia opener David Warner is fast approaching a milestone to place him among the greats, but captain Steve Smith is likely to overtake him.

Warner needs just 51 runs to become the 19th Australian to reach 5,000 in Test cricket.

And the explosive left-hander, who averages 47.58 in the five-day format, is on track to reach the mark at some rate.

If Warner manages the feat in the first innings of the Boxing Day Test against Pakistan starting Monday, he will become the sixth fastest Australian to the mark.

It would make him quicker than the likes of Ricky Ponting, Allan Border, Michael Clarke, Adam Gilchrist and the Waugh brothers.

Warner's next innings will be his 109th in Test cricket.

Fastest to 5,000 Test runs (Australia only)
56 innings – Don Bradman
95 – Matthew Hayden
105 – Neil Harvey
106 – Greg Chappell
107 – Mike Hussey
110 – Ricky Ponting

However, his stay in the top six is unlikely to be for long.

The in-form Smith, who has 4,504 Test runs and made a ton in Brisbane, is quickly approaching the same mark.

The Australia captain's next Test innings will be his 90th.

If he scores at his average of 58.49, he will become just the third Australian and 11th player in history to reach 5,000 Test runs in fewer than 100 innings.