SAN FRANCISCO — San Francisco Giants second basemen have been among the least productive units in baseball. A league-average player would represent a huge upgrade, to say nothing of a former batting champion like the Pirates’ Freddy Sanchez.

The Giants think that’s a bright idea, too, but club officials were not close to a trade that would keep Sanchez in town past Wednesday’s series finale at AT&T Park. Their first choice remains Florida’s Dan Uggla, but the Marlins are four games above .500 and have been hesitant to put their players on the market.
In the meantime, Eugenio Velez was stunningly successful while playing the keystone Tuesday night. Called up a day earlier from Triple-A Fresno and starting at second base for just the third time this season, Velez hit a solo home run in the second inning and a tiebreaking double in the sixth, leading the Giants to a 3-2 victory over the Pirates at China Basin.
At 33-15, the Giants have the best home winning percentage in the major leagues.
Nobody was suggesting Velez could be the answer to a prayer. But then again...
“He’s got all the tools,” Giants Manager Bruce Bochy said. “This guy can run, throw, he’s a switch hitter, he can play the outfield and second base all the skills you like to see in a player.”
Sanchez, for all he would cost in talent and salary, is no sure upgrade. He did not play for the second consecutive night because of left knee soreness, and sources confirmed reports that the Giants medical staff examined him Tuesday afternoon. It is not unusual, though, for an ailing player to be seen by the opposing team’s doctor on the road.
Sanchez also is stuck in a miserable 3-for-34 streak over his last eight games, sending up another red flag.
The Giants are almost certain to deal for a middle infielder, though especially after learning that shortstop Edgar Renteria will require right elbow surgery after the season. Renteria intends to play through a painful bone spur with the aid of cortisone shots, but Juan Uribe is expected to spell him often.
Giants second basemen had combined for a .585 OPS (on-base plus slugging perentage) entering Tuesday’s game; only Minnesota has received less production from second base, and the Twins were discussing Sanchez with the Pirates as well.
For one night, the Giants got some surprising power from the position. Velez’s home run into the right field arcade was just the second homer by the Giants in 12 games since the All-Star break and the fifth by Giants second basemen this season.
Velez was the starting left fielder Monday night, when he made a diving catch behind Tim Lincecum.
“He’s comfortable and relaxed out there,” Bochy said. “He’s shown good discipline, which is a key for him. He got a lot of playing time at Fresno and sometimes that’s all a guy needs.”
The Giants featured a new right side of the infield. First baseman Ryan Garko, acquired Monday from the Cleveland Indians, was cheered in each at-bat but otherwise had a quiet night. He flied out twice, grounded out and was unlucky in the sixth, when he hit a hard lineout at second baseman Ramon Vazquez.
Barry Zito survived 5-plus innings and couldn’t have scattered nine hits any better if he were Johnny Appleseed. He did not look pleased when he handed the ball to Bochy in the sixth.
“I definitely support the team, but yeah, I didn’t expect to be taken out,” said Zito, who yielded to Sergio Romo. “I support Boch’s decisions. And it worked out.”
Romo, who had been relegated to the back of the bullpen after a couple of rough outings, struck out Andrew McCutchen on three snappy pitches fastball, slider, curve.
Jeremy Affeldt gave up a run for the first time since May 7, ending a streak of 27 scoreless innings the longest by a Giants reliever in 40 years of measurable data, according to the Elias Sports Bureau.
Closer Brian Wilson pitched around Pablo Sandoval’s error to record his NL-best 26th save.