Fourth-inning leadoff man Yasmani Grandal lashed a pitch off the center-field wall against Rockies right-hander Jair Jurrjens, and center fielder Drew Stubbs quickly retrieved the ball and threw it to LeMahieu as Grandal slid into the bag.
LeMahieu's tag was slightly late, but Grandal's momentum took him briefly off the bag. In the old days, before this year's advent of the ability for a manager to make a replay challenge, infielders were taught to raise that glove to the umpire after the tag to try to "sell" an out call to the umpire. But not anymore, not with any space between the runner and the bag enough to overturn a call. LeMahieu kept his glove on Grandal.
Weiss challenged the call of crew chief and second-base umpire Ron Kulpa, and it was overturned.
The call saved a run, because the Padres' next hitter, Jake Goebbert, clubbed his first Major League homer into the Rockies' bullpen in right field to cut Colorado's lead to 2-1.
With two outs in the inning, Jurrjens threw high to first base on Alexi Amarista's short grounder. First baseman Kyle Parker leaped for the catch and came down on the bag, but the runner was ruled safe. After replay, first-base umpire Lance Barrett's call stood. Jurrjens walked the next hitter, Irving Falu, before forcing Padres pitcher Eric Stults to line to shortstop Troy Tulowitzki to end the inning.
The calls left Weiss 10-for-22 on challenges this season.
In the fifth inning, Grandal crushed a pitch from Jurrjens deep to right field with two on base. The ball appeared to sail just to the right of the foul pole and into the seats. But Grandal signaled that the ball was fair, prompting manager Bud Black to ask about the play. The umpires then huddled to review the call.
The call stood and Grandal eventually struck out.
Thomas Harding is a reporter for MLB.com. Follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.