NEW YORK -- Nothing about the New York Mets on Monday resembled the second half of last season.
Then again, opening day has often been their biggest highlight of the year.
"What a great day," Cowgill said. "We're looking forward to keeping this going."
Handed the opening day assignment in place of injured Johan Santana, Niese enjoyed a big afternoon with both his arm and bat. He breezed into the seventh inning against a Padres lineup missing slugger Chase Headley to a broken thumb and catcher Yasmani Grandal to a testosterone suspension.
"The adrenaline was pumping, I'm not going to lie," Niese said. "As far as the anxiety, it really wasn't much."
Marlon Byrd had a pair of RBI singles and fellow Mets newcomer John Buck was in the middle of three rallies as New York improved baseball's best opening day record to 34-18 (.654) despite dropping its first eight openers.
The Mets have won 20 of their last 22 season openers at home.
"So far, so good," a smiling David Wright said. "It was good to kind of bust out offensively and get some breathing room for Jon."
Niese had a perfect day at the plate himself, tying his career high with two hits. He had an RBI single in the second off an ineffective Edinson Volquez (0-1), then drew a leadoff walk and scored in a three-run fourth.
New York scored nine runs with two outs and went 7 for 14 with runners in scoring position after batting .246 in those situations last season, 20th in the majors. The three new additions to the lineup -- Cowgill, Byrd and Buck -- were a combined 6 for 14 with seven RBIs and five runs.
They provided a welcome change for a team that got off to an encouraging start last year before going 28-48 after the All-Star break in its fourth straight losing season (74-88).
"If I was going to draw it up, this would be about what it looks like and feels like," Buck said about his Mets debut. "It definitely helped me settle in a little easier."
With the Yankees hosting the rival Boston Red Sox across town, the Mets announced a sellout crowd of 41,053 at windy Citi Field, where the Padres won the ballpark's first game in 2009. The last time two New York teams opened at home on the same day was April 17, 1956, when it was the New York Giants and Brooklyn Dodgers, according to STATS.
Wright received a warm ovation when he was introduced as the fourth Mets captain since their inception in 1962. He stole two bases and made a diving play at third base in his first game since signing a $138 million, eight-year contract -- the richest in team history.
Byrd and Buck each had an RBI single in the third. Cowgill doubled to key the fourth inning, which included a run-scoring groundout by Wright and an RBI single by Daniel Murphy on his 28th birthday.
Volquez, making his third consecutive opening day start, helped the Dominican Republic win the World Baseball Classic last month. But he lasted only three-plus innings Monday and fell to 0-5 in six starts against the Mets.
"I was off a little bit," Volquez said. "I got behind in the count and they hit the ball pretty good."
The 26-year-old Cowgill, batting leadoff after winning the center field job this spring, hit his first career slam off Brad Bach in the seventh to make it 11-2. The only other opening day slam in Mets history was hit by Todd Hundley on April 26, 1995, at Colorado.
"I'm not sure I've been around a guy who competes like this guy does," Mets manager Terry Collins said. "Today was a good start for him and everybody else."
Cowgill was acquired from Oakland in a December trade. Still wearing eye black long after the final out, he acknowledged having jitters for his first opening day start in the majors. But his drive to left gave the Mets their most runs since Niese beat Philadelphia 11-1 on July 3 last year.
"Just a humbling experience today. Very grateful for it," he said.
Buck called the 5-foot-9 Cowgill "a little spark plug."
"He plays like his hair's on fire. That's what we need," the catcher said.
With his wife, parents and two brothers in the stands, Niese (1-0) gave up Carlos Quentin's run-scoring single and Yonder Alonso's solo homer before walking off to a standing ovation with two outs in the seventh. Feeling strong, the fast-working lefty wasn't thrilled about coming out of the game after 101 pitches.
"He was moving the ball around. He was throwing his cutters and curveballs for strikes," Alonso said. "He kept everybody off balance and got ahead of guys. ... So we just have to be a little more aggressive."
Mets reliever Scott Rice, making his big league debut after 14 seasons in the minors, struck out two in a perfect ninth.
"It's one of the great stories," Collins said. "I just hope he absorbed the whole thing. ... I'm real proud of him."
Touted Padres prospect Jedd Gyorko made his major league debut. He stranded four runners in his first two at-bats, then doubled in the sixth for his first hit. ... Santana, the one-time Mets ace, is scheduled for another surgery Tuesday that he hopes can save his career. The left-hander re-tore the anterior capsule in his pitching shoulder. ... The Mets honored hundreds of Hurricane Sandy responders and volunteers in a pregame ceremony. There was a moment of silence for victims of the storm and the December school shootings in Newtown, Conn. ... Rusty Staub, a member of the Mets' Hall of Fame, threw out the first pitch on his 69th birthday as the club celebrated the 40th anniversary of its 1973 pennant. ... Ike Davis went 0 for 5 with four strikeouts.