Andy Murray, the reigning US Open champion, continues his title defense on Friday against Leonardo Mayer.  The 2013 US Open second-round match is slated for 4 p.m. ET.  Watch the live stream HERE and HERE.

Murray and Novak Djokovic seem destined for a semifinal showdown.  Murray, the winner of this year's Wimbledon, can make it two straight US Open titles if he can win the tournament. 

If Murray does make it to the US Open final, which many believe he can, it's very possible Rafael Nadal would be waiting for him. 

Murray readily admitted Nadal, who's now 17-0 on hard courts this season, is the one to beat.

"It's hard not to be (impressed by Nadal)," Murray told BBC earlier in the week.  "He hasn't lost yet because he's beaten some tough players in tough tournaments, winning the two (hard court) tournaments back to back in Cincinnati and Canada.  I think it's only been done once before.  ... It's not like he's had easy draws or whatever.  He's beaten some top, top players."

Although Murray is the reigning US Open champion, he doesn't think it has any bearing on this year's tournament.

"Since we got here we've spoken about what it's like coming back to a tournament being the defending champion," Murray told the Guardian.  "It doesn't really make a whole lot of difference.  I don't think too many of the other players really care about it, when they're stepping on the court."

Murray passed his first test on Wednesday without dropping a set to Michael Llodra. 

Next for Murray is Mayer, who's ranked No. 81 in the World and is 11-15 on the season.  The 26-year-old Argentinean made it to the third round of last year's French Open and US Open.  This year, he fell in the first round of the Australian Open and French Open, and the second round of Wimbledon.

Mayer advanced from the first round of the US Open on Wednesday with a four-set win over World No. 54 Victor Hanescu.

The only previous meeting between Mayer and Murray was in 2009 at Valencia, where the Scot won in three sets.

*Stats via ATPWorldTour.com and MatchStat.com.