PHOENIX -- Diamondbacks manager Bob Melvin said Sunday that Randy Johnson's velocity may not have been as low as originally thought in Saturday night's 12-3 loss to the Royals at Chase Field.

Melvin said the ballpark's scoreboard radar gun reading was different from what the D-backs' team reading had after the Big Unit allowed eight runs (seven earned) and 10 hits in 4 1/3 innings.

"Our in-game gun was off," Melvin said. "I'm looking up and seeing 87 and 88 [mph readings] throughout the game, and we had him catching 94 and averaging 91 on our gun. I don't want to say that it plays into it psychologically, but the pitcher can't help but look up there.

"I was looking up [at the scoreboard] during the game, saying, 'It just looks like he may have a dead arm right now or he's going through a stage where he doesn't have the oomph that we've seen in his fastball,' yet I get the numbers at the end of the game and he hit 94, and I didn't see anything up there last night that would suggest he was hitting 94."

Melvin said a lot of times there is a discrepancy when a left-handed pitcher faces a lefty hitter, which can block the radar gun, adding that often the radar readings are brought down at Dodger Stadium.

"It's not like this is the only park where it happens," Melvin said. "Ours here are usually pretty consistent."

The D-backs always use their own radar for pitch speed separate from the scoreboard readings. Melvin said he got Johnson's numbers back after the game from a team employee who charted his velocity.

Both Melvin and Johnson characterized the poor outing as a case of the Unit missing with location, but both also were concerned about his supposed lack of velocity after the game -- a concern that might have been unnecessary.

"[I had] less velocity on my slider and fastball and threw too much over the plate on a consistent basis against a very aggressive team. I got hit pretty hard," Johnson said after the game.

The 44-year-old left-hander is stuck at 288 career wins. He hasn't won a start since May 18 and has lost three consecutive outings. He has allowed 17 runs in that span for an ERA of 7.71.