Gibson declined to say who would come out of the rotation to make room for Marquis, though, it would likely be Saturday's starter Micah Owings unless the team decided to shift Josh Collmenter to the bullpen.
"We're not there yet," Gibson said, adding that he planned on discussing the situation with general manager Kevin Towers and his staff following Sunday's non-waiver Trade Deadline.
Marquis, 32, was 8-5 with a 3.95 ERA in 20 starts for the Nats this year. Over 12 seasons in the big leagues he has compiled a 104-97 record with a 4.52 ERA for the Braves, Cardinals, Cubs, Rockies and Nationals.
"He's a guy that knows how to pitch, how to eat up innings and keep his team in the game," veteran infielder Willie Bloomquist said. "He's a good sinkerball guy, which will fit well in our ballpark. He's a veteran guy who knows how to pitch. I think it's a great move. He's going to go out and give you a good start every time out for the most part."
Marquis had been scheduled to start for the Nats on Saturday, but was scratched as the trade was completed just before game time. He will throw a bullpen session Monday in San Francisco before making the start Wednesday in the finale of a three-game series.
It is no surprise that Marquis will get the nod in that game, given the success he's had over his career against the Giants. In 12 games (11 starts) against them he is 5-3 with a 2.47 ERA and he is 4-2 with a 2.61 mark in seven starts at AT&T Park.
"I've always liked pitching in that ballpark, for one," Marquis said. "Ultimately it comes down to executing pitches, I've come up with pretty good game plans with some of my pitching coaches and catchers in the past. Maybe my style of pitching suits me against their lineup. I'm looking forward to Wednesday and getting off to a good fresh start, and we'll see what happens."
Marquis is coming from a last-place team to one that is battling the Giants for first place in the National League West, which raises the stakes of his first start considerably. He has pitched in the postseason five times, including the 2004 World Series.
"Anytime you pitch a big game, that's what you live for, that's why we play this game," Marquis said. "I don't mind being put in those situations, I like pitching in San Francisco and I'm just going to go over there and try to fit in. I know a lot of those guys over there have been throwing the ball really well so I'm just going to try and follow suit and do whatever I can to bring success."
Marquis was involved in a bean-ball incident with the D-backs earlier this year. He was ejected from the June 5 game after hitting Justin Upton with a pitch in the sixth inning. Warnings had been issued one inning earlier when Nats outfielder Jayson Werth was hit by a pitch and Marquis has maintained that he did not hit Upton on purpose.
Gibson said he did not expect there to be any issues between Upton and Marquis.
"There's no bad blood there," Gibson said.
"I'm a big believer what goes on on the field just stays there," Marquis said. "Obviously it was an unintentional pitch to Justin. It's part of the game. Like I said, I've been on the other end of it whether getting hit or trash talking and that's stuff that goes on on the field and that's part of the game. I don't foresee any problems. I don't know Justin personally, but I hear good things about him and we're teammates now so we're all on the same page and we're all looking forward to that one goal and that's getting to October."
While the deal was made to shore up the back of the rotation, it also served to send a message to the clubhouse that the front office is working as hard as they are to stay in the race.
"It makes us feel better because they're looking to make us a better team and keep us in the race," catcher Miguel Montero said. "He's going to be a big help for us to get a veteran arm in that rotation and I'm looking forward to catching him."
The D-backs are on the hook for a little under the $2.5 million that is left on Marquis' contract this year.
D-backs GM Kevin Towers said the D-backs still have some room to add payroll for the "right player" and he planned on working late into the night and early Sunday morning to try and acquire some relief help.