On Sunday, he showed he knew what he was talking about.
Hernandez took a no-hitter into the sixth inning against his old club, and the Diamondbacks beat the struggling Nationals 3-1 to complete a four-game sweep.
"I've got a lot of good memories here. I've got a lot of friends on the team," said Hernandez (1-0), traded by Washington to Arizona for two pitchers last summer. "I'm not the kind of guy who's going to go out there and try to beat them because I got traded last year. I go outside and do my job."
Arizona outscored Washington 21-6 in the series, and the Nationals dropped to 1-6, the majors' worst record.
"It's the first week of the season. I laugh at people who hit the panic button after the first week," said Austin Kearns, who ended Washington's 0-for-30 drought with runners in scoring position by delivering an RBI single after Hernandez left.
"Yeah, it hasn't gone good, we know that. But if we hit the panic button after the first week, come August, I guess you guys would expect to see guys hanging themselves or something."
Hernandez, who threw the first pitch in Nationals history when the Montreal Expos moved to Washington in 2005, didn't allow a hit Sunday until Ryan Zimmerman's ground-rule double with two outs in the sixth.
"He preys on guys' aggressiveness," Washington manager Manny Acta said. "He never gives in to anybody."
As usual, Hernandez mixed in plenty of pitches barely above 60 mph, along with fastballs in the low 80s. The key: keeping hitters guessing.
"Sometimes you wonder how he does it," Kearns said. "But he gets it done. I guess he's a crafty right-hander."
Said Zimmerman: "It was typical Livo."
Hernandez wound up giving up three hits over seven innings, with three walks and a strikeout. It was his 12th career victory at RFK Stadium, the most by any pitcher since baseball returned to the nation's capital.
"It seems like every time he pitches, he gives us a chance to win," Arizona manager Bob Melvin said.
Hernandez threw 105 pitches, each while holding the lead.
That's because, once again, the Nationals found themselves behind on the scoreboard before even having a chance to step to the plate. Washington's been outscored 13-0 in first innings and 22-0 in innings 1-3 this season.
This time, Shawn Hill (0-2) hit the game's second batter, Conor Jackson, on the left elbow, and Orlando Hudson's double to the base of the wall in right-center made it 1-0. Hudson took third when Ronnie Belliard's relay skipped past third baseman Zimmerman, who was charged with an error, then scored on Eric Byrnes' groundout.
Hill, though, made a strong recovery after that 2-0 deficit, and departed after 6 2/3 innings to a partial standing ovation from a home crowd that had yet to see a Nationals starter go more than six.
"Outstanding," Acta said.
But while the pitching improved, Washington's offense scored exactly one run for the third consecutive game.
Hernandez got out of a bit of a jam in the third with two outs and runners at second and third. A full-count, 74 mph pitch produced a lazy fly to center -- and made Zimmerman slam his bat.
Then, in the seventh, Ryan Church led off with a blooper to center that dropped in for a hit -- his first single of the season after six extra-base hits. Belliard followed with a lined single to center.
But Hernandez got out of it again.
Robert Fick flied to center, Dmitri Young flied to the warning track, and Brian Schneider grounded out, making Washington 0-for-6 with runners in scoring position for the game and 0-for-30 in the series. That was snapped against Brandon Lyon in the eighth; Jose Valverde pitched the ninth for his third save in four chances.
As tough as things are going for Washington at the moment, Hernandez offered encouraging words.
"It's a young team," he said. "They're going to be all right."
Arizona CF Chris Young tweaked his groin when he hit an RBI single in the eighth, then left the game during the bottom of that inning. Young didn't think it was serious; Melvin said he'll be re-evaluated Monday. ... It was the first time this season the Nationals didn't fall behind 4-0.