MLB commissioner Rob Manfred, right, stands with Washington Nationals mascot...

MLB commissioner Rob Manfred, right, stands with Washington Nationals mascot "Screech" during a news conference before an Opening Day game between the New York Mets and Nationals at Nationals Park on Monday, April 6, 2015, in Washington. Credit: AP / Evan Vucci

Alex Rodriguez wasn't the only prominent baseball figure who enjoyed a new beginning Monday.

Rob Manfred -- one of the key men in assuring A-Rod's full-season suspension for his role in the Biogenesis scandal -- beamed as he described what he felt like on his first Opening Day as baseball's 10th commissioner.

"I've always loved Opening Day," Manfred said at Nationals Park on a gorgeous day before Washington hosted the Mets. "I have to tell you, it is a materially different feeling knowing it's your first Opening Day as commissioner. I couldn't wait to come down here to Washington. I lived here for a long time and it's really particularly exciting for me to be here today."

Manfred also came to Washington on Monday to announce that baseball had awarded the 2018 All-Star Game to the Nationals.

Back in New York, Rodriguez was cheered for the most part as he played in his first game since serving his suspension. As former commissioner Bud Selig's chief deputy, Manfred was one of the leading figures in baseball's investigation of the Biogenesis matter.

And even though A-Rod is back, the performance-enhancing drug issue has not gone away. In the week before Opening Day, MLB announced 80-game suspensions for three pitchers: Ervin Santana (Twins), David Rollins (Mariners) and Arodys Vizcaino (Braves), all for using the banned substance Stanozolol.

Stanozolol is an older steroid and is considered easier to detect than some of the newer ones.

"It really is hard to explain," Manfred said. "The drug involved is one that's not particularly hard to catch . . . Performance-enhancing drugs are one of those issues where you have to stay vigilant. Things happen that you don't expect, but we have a great testing program, a great investigative capacity. If players take the risk, we feel we can catch them."

Manfred also touched on other topics, including the new metal detectors in all 30 MLB ballparks this season and have already led to fan complaints about longer wait times.

"Let's start with the most important point: We try to follow best practices from Homeland Security," he said. "We always feel that the safety of our fans ought to come first. Our experience with the screenings, given that we've been doing it some places for over a year now, is that fans adjust to the new procedures and generally find them not to be burdensome."

And as for baseball's new pace-of-game initiatives, Manfred said: "I think during spring training, we kind of eased into it. I think that process will continue as the season goes on and I think we'll become a little more aggressive as players have an opportunity to get used to the change."