The 24-year-old Arenado, a first-time All-Star last year, is 14-for-24 and has a 1.494 OPS.
"He's something else," Rockies manager Walt Weiss said. "He's been locked in since the first day of spring training."
Hill got through four innings despite walking six and allowing five runs. The left-hander has walked 12 over 7 2/3 innings and three starts.
Rockies starter Jorge De La Rosa worked out of trouble in three scoreless innings before allowing prospect Matt Chapman's two-run homer on his final pitch of the fourth. De La Rosa gave up five hits and walked two while getting 11 outs.
Athletics: Hill, who signed as a free agent in the offseason, threw only 29 of 67 pitches for strikes and saw his ERA rise to 15.26. "The feel of getting the breaking ball out of my hand has been an issue," Hill said.
Rockies: De La Rosa wasn't as sharp as when he went three perfect innings in his last start. He threw 47 of 63 pitches for strikes and struck out two. "My control wasn't there, but I was able to get the outs when I needed them," De La Rosa said.
Athletics: RHP Henderson Alvarez threw another bullpen session in his recovery from shoulder surgery.
Rockies: INF Daniel Descalso will be out several weeks after an MRI revealed a broken bone in his non-throwing hand. "He's rubbed off on a lot of people around here," Weiss said of the veteran utility player. . LHP Tyler Anderson (strained oblique) is expected to miss several weeks.
WHAT A STORY
Trevor Story entered camp a long shot to be Colorado's opening-day shortstop. It's not so improbable anymore.
The 23-year-old started again and batted second with Colorado's mostly "A" lineup. He was 0-for-2 with a walk and made a fine backhand on a tough hop to start a double play. Story has four home runs and is hitting .318.
The Rockies need to replace Jose Reyes, who's on paid leave while facing domestic violence charges.
"I knew I finished (last year) in Triple-A and with Jose being out someone was going to have to fill his spot for a little bit," Story said. "I just treated it as come in and have fun and not worry about winning the job."
Oakland's Sam Fuld made a spectacular diving grab of D.J. LeMahieu's liner to right in the second and threw to second in time to get Ryan Raburn out.
THAT WAS WEIRD
A false fire alarm at the end of the eighth triggered an automatic recording to play over the public address system that told fans to leave the stadium. The Rockies delayed taking the field for the ninth, but eventually did and many fans returned to their seats.
Rockies: RHP Chad Bettis starts Wednesday against the Los Angeles Dodgers. The Rockies announced prospect Jeff Hoffman, acquired in the Troy Tulowitzki deal last summer, will start Thursday against the Los Angeles Angels.