The Ravens have never lost four straight games during John Harbaugh’s eight-plus seasons as head coach. Even last year, when the Ravens went 5-11, their longest losing streak was three games.

So with the Ravens (3-3) riding a three-game losing streak heading into their Week 7 road game against the Jets, there is obvious reason for concern. Here are three challenges the Ravens face in their attempt to get their season back on track.

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1. Injuries to key older players

Right guard Marshal Yanda (shoulder), wide receiver Steve Smith Sr. (ankle), outside linebacker Terrell Suggs (biceps) and Elvis Dumervil (foot) are all dealing with injuries. All of them are tough, but all of them are over 30 years old, when injuries tend to happen more frequently and often take longer to heal.

It doesn’t sound like Yanda or Suggs will play against the Jets, and it sounds like Dumervil will be out for awhile. Trying to win without them will make ending this current losing streak more difficult.

2. Penalties

The Ravens are tied with the Raiders for the NFL lead in penalties with 52. Nobody had more penalties in Week 6 than the Ravens, who were called for a whopping 15 during their loss to the Giants. That’s inexcusable. Point the finger at whoever you want between the coaches and players. But unless the Ravens reduce their self-inflicted mistakes, it’s not logical to expect them to win consistently.

3. The most challenging part of the schedule lies ahead.

It remains to be seen if Steelers quarterback Ben Roethlisberger (torn meniscus) will be healthy enough to face the Ravens in Week 9. But Steelers-Ravens games are usually close, regardless of who plays. The Ravens have two games against the Bengals, who are struggling at 2-4. But the Bengals have beaten the Ravens five straight times. The Ravens also face road games against the Patriots and the Cowboys, who are both 5-1.

The Ravens had a golden opportunity to be 5-1, or at least 4-2, after their 3-0 start. Instead, they are at .500, and trending in the wrong direction.

The Ravens’ immediate concern is beating the Jets (1-4), who have even bigger issues. But the Ravens have never lost four straight under Harbaugh. If that changes Sunday, it will be another ominous sign.

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