Early round upsets aren’t all that unusual at Wimbledon, which opens its two-week run tomorrow. Last year, Rafael Nadal, fresh off his eighth French Open title, was bounced in the opening round by unheralded Steve Darcis of Belgium. Roger Federer fell several days later in a second-round upset at the hands of Ukrainian Sergiy Stakhovsky. The year before, Nadal met his Waterloo in the second round. Czech Lukas Rosol was the dragon slayer that time. After perusing the men’s draw on Friday, I selected five first-round matchups rife with upset potential. The tournaments and results cited below, all on grass, factored somewhat in my picks. There’s a lot of hunch too. Nadal’s opener tops my list. The No. 1-ranked Spaniard and second seed, plays dangerous Slovak lefthander Martin Klizan. Klizan reached the quarterfinals at Eastbourne earlier this week, before losing to finalist Richard Gasquet. Nadal was shellacked in the first round at Halle the week before by German Dustin Brown. Rafa could be ripe for his fourth straight loss on grass. No. 2 on the list is Japan’s Kei Nishikori, the No. 10 seed, versus tough lefthander Kenny De Schepper. The 6-foot-8 Frenchman lost to Eastbourne winner Feliciano Lopez in three tiebreakers in their third-round encounter this week. De Shepper’s serve is perfectly suited for grass and he could surprise. No. 18-seeded Fernando Verdasco may find himself in a real dogfight with Australian Marinko Matosevic, who beat Marin Cilic and Jo-Wilfried Tsonga en route to the quarterfinals at London a week ago. The week previous, Matosevic reached the final of the Nottingham Challenger. The fourth dodgy call is the contest between Tsonga, seeded 14th, and Austrian Jurgen Melzer. Melzer lost to ‘s-Hertengobosch champion Roberto Bautista-Agut in a third-set tiebreaker in the semifinals on Friday. Tsonga isn’t at peak performance at the moment so I give Melzer a good shot. The final matchup is a bit of a stretch, No. 19 seed Alexandr Dolgopolov against big-serving Sam Groth. Dolgopolov has had just two matches on grass in the lead-up and retired in a third. Groth lost to fellow Australian Nick Kyrgios in two tiebreakers in the final of the Nottingham-2 Challenger a week ago, but never lost serve in the tournament. He won three matches to qualify for Wimbledon and is 7-1 on grass this year. Can’t help but think there’s an upset or two in these five pairings.