"I think the one guy we look to who is probably the most experienced and has been through a lot is Edinson," Mattingly said. "But I don't really know if we have to really say anybody is our No. 1."
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Volquez, 33, was the Marlins' most significant free-agent addition this offseason, signing a two-year, $22 million contract in December.
In 2015, he was part of a World Series championship team with the Royals. And he was Kansas City's Opening Day starter in 2016.
The Marlins don't have a clear-cut ace. Wei-Yin Chen started the opener for Miami in 2016.
"That's a great opportunity for me," Volquez said. "If he said it, I'll take it. But we have five guys in here trying to do their best to be in the rotation and be a No. 1 or No. 2. It doesn't matter where you pitch, you've got to pitch every fifth day. For me, it's a great honor to be here."
Volquez has a 89-79 record with a 4.44 ERA in 259 career games (252 starts). The right-hander had a rough 2016 with the Royals, going 10-11 with a 5.37 ERA. He has been highly durable in his career, and he logged 189 1/3 innings in 34 starts in '16.
"Not many teams have that pure ace," Mattingly said. "They may have a guy they say is their No. 1, or they call their No. 1.
"I think a lot of our guys are similar. But Edinson is our guy who probably is the most experienced. He's been through the most. He's won a World Series. He's pitched in high-impact games. He'd be the one guy, I think, who would be our guy who has handled all different situations."
Volquez took the field for the first time as a Marlin on Tuesday. As drills were winding down, he admittedly was running out of steam, and he said so to Mattingly.
"I got tired a little bit," Volquez said. "Like I told him, 'Hey, he can have his money back.'"
Mattingly laughed and assured the veteran right-hander that he'd be fine.