Two matches take my fancy tonight and I expect them both to be full of tension and drama.

Kei Nishikori vs Juan Martin del Potro

At 18 and 19 years old respectively, Nishikori and del Potro are the youngest players left in the tournament and they are taking the tour by storm. I have rated Nishikori extremely highly for the past year or so, and it is a breath of fresh air to see his aggressive style of play reaping rewards on the hard court. His trademark 'flying forehand' is nothing short of exhilarating and the Japanese teenager is bound to become a superstar in his homeland.

Del Potro is on a record-breaking 22 match winning streak, and has defied those who thought that his poor fitness would mean that he would be fodder in a best of five sets match. Nishikori has also proved his critics wrong, and in fact displayed remarkable levels of fitness in his third round victory over fourth seed David Ferrer, who by all accounts is a specialist in five set matches.

Del Potro is currently trading at about 1.3 on the exchanges, and it's hard to argue with that. His style of play should match up well to Nishikori's and it is tough to oppose someone on an outrageous winning streak. However, Nishikori has the talent and belief to push del Potro to the limit, and I expect that the Argentine will trade much higher in-play. Therefore, I'm very interested in SkyBet's total games market. They have set the bar at over/under 38.5 games, which would have copped in all of del Potro's matches so far, and one of Nishikori's. In what should be a close encounter over four or five sets, I'm happy to take on the bookies here.

This should be an incredible match, and I would highly recommend staying up 'til the wee hours to view what could be a classic. I'll also stick my neck out and say that both players will be permanent fixtures in the top 5 over the next few years. Either way, a star will be born.

Stanislas Wawrinka vs Andy Murray

Britain's no. 1 takes on one of his best friends on tour in Stanislas Wawrinka for a place in the quarter-finals. With the H2H level at 3-3, there is little to pick between these two players, but  to me, it's clear that Murray has the edge. In picking up his maiden Masters Series in Cincinatti a few weeks ago, Murray proved his pedigree and a place in the top 5 beckons. Wawrinka is hugely talented but has failed to push on after an encouraging clay court season. The Swiss maestro hit a massive 81 unforced errors in a five set marathon against lucky loser Flavio Cipolla, underlining that he is not in the greatest of form.

Compare this to Murray, who only conceded 29 UE's in his five set match against Austria's Jurgen Melzer. Murray has the edge on hard courts, and his defensive qualities mean that Wawrinka will always struggle to break him down. This is reflected in their previous hard court meetings, with Murray leading H2H 3:1, winning the last three in a row.

However, none of these matches have been in straight sets, and having dropped sets to Michael Llodra and Melzer so far, I think that Murray will struggle to win this 3-0. His superior confidence and fitness should see him through this match, but we are reluctant to back 1.4 on him to win the match - instead, the value is surely in dutching him to win 3-1 or 3-2 at combined odds of 2.64.

NJ's Bets:

Nishikori/del Potro over 38.5 games - 3pts @ 1.83 (SkyBet)

Andy Murray to win 3-1 - 1.75pts @ 3.75 (SkyBet)

Andy Murray to win 3-2 - 0.75pts @ 9.0 (Sportingbet)

(Player stats from www.atptennis.com)