"Right now depth is a big key to our success," Upshall said. "Our last ten games we've had everyone except [Joffrey] Lupul healthy, and he's been a big part of our team."
Lupul, who has missed the last seven games, is out indefinitely after sustaining a mild concussion and spinal cord contusion at Toronto on Jan. 5.
Hartnell, who was acquired from Nashville with Kimmo Timonen in a trade last June, has scored ten goals in the last seven games and 16 in the last 28 games, after going without a goal for the first 15 games of the season.
Hartnell also made good on a pre-game prediction.
"Hart's [Hartnell] been on fire lately, so to speak," Upshall said. "Tonight he actually said, '[I feel] it's going to be my night tonight.' Being the good buddies that we are, it was a big win for us."
Chris Kelly scored for the Eastern Conference-leading Senators, who have lost two in a row and four of their last five.
Ottawa was again without its two leading scorers. Daniel Alfredsson (29 goals, 31 assists) has missed two games and is day-to-day since injuring his hip against Carolina on Thursday, and Dany Heatley (25 goals, 31 assists) is out indefinitely after hurting his right shoulder against Detroit on Jan. 12.
"Two big key guys out of the lineup," Kelly said. "When that happens, it gives other guys an opportunity to play more and contribute more. For those guys, they haven't done that so far."
Ottawa coach John Paddock echoed Kelly's sentiments.
"I was disappointed in some individuals that are not taking advantage of stepping up," Paddock said. "They're not being responsible in doing the right thing."
Flyers backup goaltender Antero Niittymaki, who hasn't lost in regulation in his last seven starts (6-0-1), made 25 saves. His only loss during that span came against Boston, 4-3 in overtime.
Ottawa's Martin Gerber allowed four goals on 14 shots before being replaced by Ray Emery at the beginning of the third period.
Coburn put the Flyers ahead 1:37 into the first period when he scored on a one-timer from just beyond the slot. Then Hartnell made it 2-0 at 13:16 of the period when he converted another one-timer from the front of the left circle after taking a pass from Jeff Carter.
The Flyers increased their lead to 4-0 by scoring on their first two shots of the second period. Upshall snappped a wrist shot from the left circle at 0:44, and Umberger scored on a goal mouth scramble at 3:50.
Kelly made it 4-1 at 7:27 of the period on a wrist shot from the right circle over Niittymaki's blocker, but Kapanen put in a rebound of Coburn's shot to score short-handed at 3:49 of the third period. Upshall added his second goal on a two-man advantage at 17:52.
Kapanen said that the Flyers are starting to jell at the crucial time between Christmas and the All-Star break.
"Having many new players it takes probably three to four months to get together and start clicking as a team," Kapanen said. "Going into the stretch was huge for us, and so far we're doing pretty good."
The Senators played the first of a four-game road trip. ... Ottawa C Randy Robitaille played his 500th NHL game. ... Ottawa RW Brian McGrattan left the game after hurting his right shoulder in a fight with Riley Cote early in the first period. ... The Flyers, who lead the NHL with 57 power play goals, were 2-for-7 with the man advantage.
Copyright by STATS LLC and The Associated Press
Arena: Wells Fargo Center Location: Philadelphia, Pennsylvania
Referees: Brad Meier, Tim Peel Linesmen: Scott Driscoll, Andy McElman