While playing for the San Fransisco Giants, the new Washington Nationals' manager Matt Williams would do impersonations of Babe Ruth, including waddling around the bases and stuffing a pillow underneath his jersey. (MLB Advanced Media, L.P.)

Behind the intense gaze and concentration, the meticulous planning, the reputation he built as a clubhouse enforcer, Washington Nationals Manager Matt Williams has a goofy side. He just doesn’t show it often. As a player, he may have stood up to teammates such as Barry Bonds and Kevin Mitchell, but he was also popular for his ability to make fun of them and laugh at himself.

Early in his career, Williams was known for his impersonations of teammates and baseball greats. A 1990 Chicago Tribune article referred to Williams, at the time the San Francisco Giants’ third baseman, as being “renowned throughout the National League as a master of baseball impressions.” His manager, Roger Craig, said then that Williams could do an impression of “just about anyone.” Williams would perform on demand.

Williams imitated Reggie Jackson’s swing and how Jackson watched his home runs from the batter’s box. He copied teammate Will Clark’s swing and high-pitched voice. He impersonated the unique pitching deliveries of teammates Rick Reuschel and Mike Krukow. Williams even imitated past managers’ mannerisms — but out of their sight. He imitated Babe Ruth and, before a 1991 game, television cameras caught Williams with a pillow under his jersey, waddling around the bases and waving at imaginary fans in the stands.

“I don’t know if it was skill,” Williams said recently. “Billy Crystal and those people have skill. I’m just fun. I like to have fun.”

Six months and six regular season games into his tenure as Nationals manager, Williams, 48, has exhibited some of the qualities he showed as a player. “He’s an intelligent, aggressive personality that knows the game inside and out,” General Manager Mike Rizzo said.

But Williams has also shown glimpses of his lighthearted side. Before his first spring training game, he tried snapping photos with his cellphone of a coach sleeping on the bus so that he could embarrass him later. During camp, he asked a reporter to send him a funny photo of bench coach Randy Knorr from last season so he could post it in the coaches’ office. First baseman Adam LaRoche, who loves pranks, said Williams is helpful when brainstorming.

“He’s a pretty good combination of very intense but knows when to let off and drop a joke every once in a while,” LaRoche said.

“Matt has a great personality,” Craig, 84, added in a telephone interview. “Very witty, very sharp. As well as being a great baseball person. He was tough in the way he played but he didn’t do it with his imitations and stuff like that.”

Williams’s most memorable impression was that of Ruth. While the team was on the field for batting practice on June 23, 1991, for a game against the Chicago Cubs at Candlestick Park, local television cameramen asked Williams to do his Ruth impression to air during the game broadcast. It was also a turn-back-the-clock game, and the Giants were wearing the old New York Giants uniforms. It was only fitting that Williams re-enact Ruth. “I was young,” he said recently with a smile.

Williams had a famous clip of Ruth ingrained in his memory. Ruth, a left-handed hitter, swats a home run, the crowd goes wild, the beer-bellied slugger waddles around the bases and waves his cap after he rounds second. Williams, a right-handed hitter, found a pillow and stuffed it under his white Giants jersey. A video clip unearthed and provided by Comcast SportsNet Bay Area shows Williams swinging left-handed, dropping his bat and hobbling around the bases with short steps like Ruth, his arms churning furiously. Williams also waved his cap.

“There’s some footage of it where the story goes that Ruth was taking ribbing from the other dugout,” Williams said. “And supposedly he called the shot, hit the ball over the fence and waved fans back saying, ‘You can sit down now. I did what I told you I was going to do.’ ”

As a youngster, Williams would stand in the backyard imitating the swings of famous hitters. He watched enough television to perfect an impersonation of broadcaster Howard Cosell. Williams often copied Clark’s high-pitched voice. When Williams took the field, he sometimes pushed out his ears, a reference to Craig’s big ears.

“It would crack everybody up,” Craig said. “Maybe in a crucial moment of the game when we needed it he’d do that. If it was a tight ballgame, he tried to get everyone relaxed.”

In his rookie season with the Giants in 1987, Williams imitated Craig’s mannerisms, walk and talk but only among teammates out of fear of getting in trouble. But celebrating in the clubhouse after the Giants won the National League West, teammates asked Williams to perform publicly.

“They asked me to get up on the table to imitate Roger Craig.” Williams said. “I had to do that. I believe he was there. In front of my teammates. It was quick, but I wasn’t sure if I was going to be back in the big leagues for imitating the manager.”

“I don’t remember too much about that because of the champagne,” Craig said.

Few, if any, in the Nationals clubhouse knew of Williams’s goofy past. Shown the clip of Williams’s Ruth impression, hitting coach Rick Schu chuckled. “Pretty good,” he said. Does he look like Ruth? “Absolutely!” said Mark Weidemaier, the team’s defensive coordinator and advance coach. “Matt did it perfect,” Craig added. LaRoche laughed so much when he saw it his face turned red. “That was awesome. I didn’t know he had it in him.”

Talking about his past impressions, Williams is self-deprecating. He refers to himself as “impressionable” and adds that he had “too much time on his my hands” back then. Later in his playing career, Williams stopped doing the impressions. He does admit, however, that he is working on his impression of the boisterous Weidemaier. Williams hasn’t performed his best impression, the one of Ruth, in more than 20 years.

“The last time I did the Babe Ruth impression was in that footage,” he said. “I had hair back then even.”