Big-serving Sam Groth’s very good week came to an end yesterday when American grinder Michael Russell defeated the strapping Aussie with arm tatoos 7-6 (3), 7-6 (1) in the semifinals of the Knoxville Challenger. Groth, holder of the record for fastest serve in the game, couldn’t quite put away the scrappy Russell who forced the 25-year-old career journeyman to work harder than he had all tournament. Groth became a bit of a sensation in May when he blasted a 163-mph (263 kph) ace in a Challenger match at Busan, South Korea. The feat shattered the previous mark of 156 mph by Ivo Karlovic. Ranked No. 245 in the world, Groth buzzed through his first three matches in Knoxville with relative ease, hitting 60 aces and winning 86 percent of the points on his first serve. Things were different against the 34-year-old Russell, who is still in super shape and can run his opponents ragged. Groth did hit 12 aces, but for a server of his prowess won only a pedestrian 70 percent of his first service points. The 6-foot-5, 230-pound Aussie — the ATP Tour website conservatively lists him at 6-4, 205 lbs. — was broken three times, twice in the first set, and failed to win a point on his serve in the second set tiebreaker. Russell, ranked No. 103, also was broken three times but had Groth gassed at the end. “He’s got a cannon,” Russell said. “It’s so tough to play Sam. He serves so big, and from the ground, he’ll spin, spin, and all of a sudden he’ll crush a backhand. There’s not a lot of rhythm, so you feel so much pressure on your own serve. I’m really pleased to get through that.” Russell plays Bobby Reynolds in today’s final. With the 29 points he picked up for reaching the semifinals, Groth will achieve a career high tomorrow when the ATP computer updates its rankings. That fact was not lost on the big Aussie when he Tweeted yesterday: “Went down 6 and 6 to Russell today, disappointed but a good week to finish the year that will result in a career high next week.” Groth got to No. 220 on Nov. 16, 2009.