The left-handed Hosmer, MLB.com's No. 8 overall prospect, connected on Round Rock lefty starter Zach Jackson's 3-2 fastball in the first inning for what eventually was ruled a two-run longball.
But despite the power surge from Hosmer and another shot five innings later by fellow Royals prospect Clint Robinson, the Storm Chasters were upended by the hosting Express, 7-5.
Hosmer wasn't sure he had cleared the 8-foot right-center field wall in The Dell Diamond, so he slid into third and was tagged out. But Omaha skipper Mike Jirschele was more convinced. After Jirschele emerged from the visiting dugout and the umpiring crew agreed to discuss the call, Hosmer crossed home plate.
The dinger barely cleared the wall's yellow line and landed in an area marked in white paint just above it, according to Hosmer.
"It's good to get the first one out of the way," he added, laughing at the turn of events that led to it.
In 2010, the former No. 3 overall Draft pick homered for the first time 11 games into the season, but didn't record his second one until game No. 36. He ended up with 20 for the year.
Cognizant of the fact that he plays first base, a corner infield position often manned by power hitters, Hosmer said he doesn't feel pressure to clear another fence soon -- even if it's by mere inches.
"When I'm struggling, the worst thing I do is get anxious and try to do too much," he said. "When I'm going good, I'm just staying through the middle [of the field] and trying to hit line drives. And the home runs come. I can't try to hit the home run."
Following the 1-for-4 performance, his batting average fell slightly to .314. Meanwhile, the Storm Chasers have dropped four straight games.