There are eight ties scheduled for this weekend in the World Group first round of the Davis Cup. Several of them could hinge on the doubles rubber to give one country or the other a key advantage. Here is a quick look at two of the doubles rubbers that could swing the momentum of their respective ties.

Australia vs. USA

One of the highlight matches of the weekend could be in this tie. This afternoon's news regarding Lleyton Hewitt's inclusion in Australia's lineup for the weekend has only added to the buzz. Only one thing seems certain at this point in that tie and that is that the Americans will roll out Bob and Mike Bryan for the doubles rubber on Saturday. Australia has plenty of decisions and intrigue to make on its side in the wake of a viral illness that will keep Nick Kyrgios out of this weekend's tie.

The Aussies now have Bernard Tomic, Hewitt, Sam Groth and John Peers all named to their squad. Most had expected Groth to pair with Peers in doubles. Now, that may be a big question. Peers has no previous Davis Cup experience, whereas Groth and Hewitt played a integral role in Australia's semifinal run last year. The duo won a key doubles rubber in the quarterfinals - Kazakhstan and lost a heart breaker in five sets in the semifinals to Andy and Jamie Murray of Great Britain.

One scenario could see Groth being pushed into singles duty. He's 3-0 on grass and more than capable of putting up a good fight against John Isner or Jack Sock on that surface in front of a raucous home crowd. That seems more likely than trotting Hewitt out for singles duty with Hewitt not having a competitive match under his belt since his run ended at the Australian Open. More information on that decision will come on Thursday or Friday.

Whatever the combination is, the Aussies will feel they have a chance against the Bryans, who have continued to scuffle on the ATP World Tour this season. The American twins are just 4-4 this season on tour. The Bryans have won three straight in Davis Cup play though after losing two straight in 2013.

Germany - Czech Republic

This figures to be an extremely competitive tie in Hannover on an indoor hard surface. Both sides sent out solid singles players with the Germans looking to Philipp Kohlschreiber and young phenom Alexander Zverev. The Czechs turn to Davis Cup stalwart Tomas Berdych and Lukas Rosol. That could leave the doubles rubber in this one as a huge momentum swinger. The doubles nominees are Dustin Brown and Philipp Petzschner for the home side. Jiri Vesely and Radek Stepanek are in line for the visitors.

It would be no surprise at all to see some substitutions made to those possible duos. The Czechs may well turn to Berdych, who is 20-2 in doubles rubbers all-time. Berdych has subbed in the last four times he has played a Davis Cup tie, in order to team with Stepanek. They are 3-1 together in that span with the lone loss coming in last year's semifinals against France.

The Germans could look to Kohlschreiber's experience to pair with Petzschner. That is the exact scenario that played out in the World Group playoff in 2015 against the Dominican Republic. Kohlschreiber and Petzschner paired up to win the key doubles rubber that gave the Germans a 2-1 lead. They would wrap up the tie with Kohlschreiber winning his second singles rubber of that weekend.

Second Seeds Exit in Open Round at BMW Malaysian Open

Darija Jurak and Nicole Melichar were the final seeds to play their opening round match in Kuala Lumpur. They are one and done after being beaten 7-6 (5), 6-1 by Zarina Diyas and Yi-Fan Xu. The unseeded duo came back from an early break down to get back on serve with a break in the 7th game of the opening set. They would push the set to a tiebreak, where they would rally back from a 3-1 deficit to capture the breaker 7-5. The second set saw them coast as Jurak-Melichar struggled with their serve. The second seeds landed just 40 percent of their first serves, allowing Diyas and Xu plenty of looks at weaker second serves. Diyas-Xu would take 10 of 12  second serve points and break their opponents three times in the final set.

Yafan Wang (right) delivers an overhead smash (Photo: Getty Images)
Yafan Wang (right) delivers an overhead smash (Photo: Getty Images)

Fourth seeds Alexandra Panova and Marina Melnikova joined Jurak-Mellichar on the sidelines. Panova and Melnikova were taken out in the quarterfinals by Katarzyna Piter and Maryna Zanevska 6-2, 6-7 (2), 10-8. In other action, the top seeds avoided the same fate of the other seeds. Chien Liang and Yafan Wang edged Kai-Chen Chang and Oksana Kalishnikova 4-6, 6-3, 10-5. Liang and Wang will take on Piter and Zanevska in the semifinals.

Spaniards Roll in Monterrey

Top seeds Anabel Medina Garrigues and Aranxta Parra Santonja continued their good form on Wednesday. The Spanish duo won their first round match at the Abierto Monterrey 6-1, 6-3 over Marina Erakovic and Silvia Soler-Espinosa. The win marks the fifth straight for Medina Garrigues and Parra Santonja. The only other match completed during the day saw Nicole Gibbs and Tatjana Maria pull off a minor upset. Gibbs and Maria defeated Christina McHale and Xinyun Han 7-6 (7), 4-6, 10-8. Third seeds Kiki Bertens and Johanna Larsson were scheduled to finish off Wednesday's schedule late in Monterrey. They take on Victoria Rodriguez and Renata Zarazua in the final match scheduled on Cancha Central.