Tennis Week blogger Brad Gilbert has been monitoring the matches at last week's Sony Ericsson championships in Doha as well as watching the race for the final place in the ATP World Tour finals heat up and shares his insight in his latest blog.

BG believes the Williams sisters, who were the last women standing in Doha, not only showed their staying power in dueling for the season-ending title, but will both be forces on the WTA Tour for another three to four years.

"At 28 and 29 years old respectively, Serena and Venus show no signs of slowing down when so many of their peers have fallen by the way side," BG writes in his Brad Gilbert Unplugged blog. "Their careful schedule  and increasing their doubles play seems to help them maintain more motivation. And I see no reason why they can’t carry on this way for another three or four years."

Brad also offers his views on the men's race to London and identifies how Roger Federer's new addition will help his cause.