Randy Moss and Wes Welker are a great combo, but the Patriots don't have much to back them up at wide receiver.

Journal photo / Mary Murphy

So far, so good.

The Patriots are sitting atop the AFC East at 5-2, and if the playoffs started this weekend, the team would be, as Bill Parcells likes to say, “in the tournament.”

But there’s still a long way to go — more than half the season — and the Pats appear to be walking a perilously thin tightrope on their path to postseason play.

With two weeks to prepare for the currently 2-4 Dolphins, it’s not unreasonable to think the Patriots will be 6-2 at the midway point of the season.

Although, lest we forget, the Dolphins had lost 20 of 21 when last they visited Gillette Stadium, while the Patriots had won an NFL-record 21 straight regular season games. Yet the Dolphins, unveiling their innovative — in part because it was so old-fashioned — “Wildcat” formation, befuddled the Pats en route to a stunningly easy 38-13 victory.

Still, a New England win nine days hence is to be expected, which would leave the Pats in a solid position at the midway mark.

Yet they seem to be in somewhat shaky shape for the second half.

It would be inaccurate to say they’re in deep trouble. But it’s certainly true that they have serious depth problems at critical positions.

Stating the obvious, if superstar quarterback Tom Brady goes down, the Pats’ playoff hopes go down with him. They have survived almost half the season with only undrafted rookie free agent Brian Hoyer in reserve, which seems very much like a football version of Russian roulette.

Especially given that Brady currently can count on only two quality — albeit exceptionally high-quality — receivers in Randy Moss and Wes Welker. Furthermore, the team’s offensive line has not been dominating, and the running game too often has been more reminiscent of the days of Reggie “One-Yard” Dupard than of Sam Cunningham, Craig James, or Corey Dillon.

Other than Brady, who threw for six touchdowns — five of them in the second quarter — in the Pats’ 59-0 trouncing of Tennessee two weeks ago, Moss is the main man in the New England offense. He is the Patriots’ only serious deep threat. Teams that don’t double him risk a touchdown any time he’s 1-on-1 with even their best defender.

When Moss does draw double coverage, that makes it easier for the elusive Welker to find open space in the secondary, where Brady unerringly puts the ball in his sure hands. In addition, veteran Kevin Faulk is very capable at moving the chains as a receiver coming out of the backfield.

Welker and Moss each has more than twice as many receptions as anyone else on the team. Welker is the leading receiver — not just in New England, but the entire NFL — in number of catches, with 46 for 484 yards and 4 touchdowns, despite missing two games with a knee injury. But Moss — as you’d expect — leads the team in receiving yards, with 565 on 43 catches, also with 4 TDs.

Moss, however, clearly was favoring his left shoulder in the Patriots’ 35-7 rout of 0-7 Tampa Bay last Sunday in London. If he’s ever out of the lineup, New England’s deep threats — and that term, in this case, is used loosely — would be Sam Aiken, who caught his first touchdown pass in seven NFL seasons against the Bucs, and rookie Brandon Tate, who was activated only last week off the Physically Unable to Perform list, following reconstructive knee surgery midway through his senior season at North Carolina.

Promising rookie Julian Edelman, successfully converting from having been a quarterback at Kent State to a wide receiver in the NFL, is sidelined with a broken arm. Tight end Ben Watson is tied with Moss and Welker for the team lead in TD catches, with 4, among his 15 receptions. But it will be much harder for everyone to get open if Moss is at much less than his best or, heaven forbid, sidelined by injury.

And it’s not as if the Patriots can count on pounding away at people on the ground. Although their average yards per carry are good — even the oft-criticized Laurence Maroney is averaging 4.3 per attempt, in part because of a 45-yard TD scamper against the terrible Titans — New England’s running game does not strike fear into opposing defenses.

What’s worrisome now is that both Fred Taylor and Sammy Morris are sidelined by injuries, leaving only Maroney, BenJarvus Green-Ellis, and the 33-year-old Faulk available to carry the ball.

Protecting Brady is, of course, paramount to the Patriots. Which is why rookie left tackle Sebastian Vollmer, filling in for the injured Matt Light, picked up two holding penalties in the same drive last Sunday against the Bucs. He said he’d rather pick up a penalty than have to pick up Brady after he’d been blindsided.

The usually-reliable Logan Mankins was penalized four times against Tampa Bay — three of them for false starts, the other for holding. Veteran center Dan Koppen also was flagged for a false start.

The Pats aren’t likely to be able to get away with mistakes like that against the likes of the Colts and Saints, both of whom they’ll be facing on the road in November. That said, those teams are the only two of New England’s remaining nine opponents against whom the Patriots won’t be favored.

Assuming, that is, that their already perilously thin ranks are not further depleted — a huge assumption given that more than half the season remains.

If Brady, Moss, and Welker remain healthy, the Patriots’ playoff prospects will be robust. But there seems to be no margin now for error, and lot of football yet to be played.

So far, then, so good. But there’s still a lot of football left to be played, and the Patriots don’t have any players left to spare.

jdonalds@projo.com