The Flyers have won four straight and hold second place in the Metropolitan Division.
"There's lots of talented teams in the National Hockey League, but that team is fully invested in checking," Hitchcock said. "You see it in their penalty killing. You see it in their forecheck, their five-on-five play. They are going to be a bear in the playoffs."
While Hitchcock was praising the Flyers (37-25-7), coach Craig Berube was raving about the Blues (47-15-7), a hardworking team that has an active forecheck and an NHL-best 101 points heading into Friday.
"They're a structurally sound hockey team," Berube said. "Good size. Physical team. Pretty solid all around."
To beat St. Louis, Berube said, the Flyers have to play better than they did in their 4-2 win over Dallas on Thursday.
"The second period was sloppy and we turned pucks over," he said. "We didn't really get engaged or involved in the second period at all along the walls."
The Blues are built around an outstanding defense and balanced scoring. Their top scorer, Olympic hero T.J. Oshie, is tied for 36th in the NHL with 54 points.
"We know we don't have maybe the top-end guys that some other teams do, but we are very much the sum of our parts," said Hitchcock, who will be coaching his first game in Philadelphia since he took over the Blues in 2011-12. "Our leaders don't allow our team to dip very far or for very long; they've got a full grip on the team. That's one of the reasons we've been consistent.
"Our leaders are willing to talk about the hard things that have to be discussed without the coaches being involved. We expect a lot out of ourselves, but the players are driving the bus."
Goalie Ryan Miller has excelled since being acquired Feb. 28 from Buffalo, along with pesky forward Steve Ott.
"It wasn't just Ryan Miller we wanted. We really wanted to get our hands on a guy like Steve Ott, who to me is built for the playoffs," Hitchcock said. "He's a guy who has really added to our team. It was a combination of Miller-Ott that we felt we needed to take a chance on to help our team to the next level."
Oshie gives the Blues an edge if the game goes into a shootout.
"What he did in the Olympics was an unbelievable display of talent in an extremely high-pressured situation," said Flyers goalie Steve Mason, referring to Oshie's four shootout goals that enabled Team USA to defeat Russia, 3-2, last month.
The Flyers, winger Scott Hartnell said, have focused on "cleaning up our game in areas - turnovers, bad penalties, things like that. I like where we're going, and this will be a big test for us."