New England Patriots tight end Rob Gronkowski was held to four catches for just 51 yards Sunday night against the Detroit Lions. (Paul Sancya/Associated Press)

It doesn’t take an expert to see the New England Patriots' offense is struggling. Not just anybody can lose to the Jacksonville Jaguars and Detroit Lions in back-to-back games.

One measure of the offense’s woes: Over the past two weeks, quarterback Tom Brady has targeted Rob Gronkowski nine times. Six of those attempts have been completed for a measly 66 yards. Gronkowski has played 56 games in his nine-year career with better output than that.

At least one person can tell those difficulties are getting to Gronkowski: his brother Chris, who played three seasons as a fullback with Dallas, Indianapolis and Denver.

He called in to the WEEI sports talk radio show “Kirk and Callahan” on Tuesday to complain that the Patriots lack offensive weapons and that too much of the burden is falling on his brother, the four-time all-pro tight end.

The Lions double-teamed Gronkowski in the game’s big moments and made Brady throw to less experienced targets.

“When you’re giving up two of your best defenders — safeties or a corner and a safety — to cover a tight end, guys on the outside should be able to win,” Chris Gronkowski told the popular Boston station. “It’s just super frustrating to watch. They’ve got to figure something out."

“I haven’t talked to him personally about it,” Chris Gronkowski added, “but I can just tell by his emotions, his facial features, that he’s super frustrated with it. You can see at the end of the game how they ended the game double-covering him, pressing him off the line. He just wants to get the ball in his hands and make plays. But you just can’t do it when nobody else is getting open. You can’t have single coverage [on Rob Gronkowski] if no one else can beat single coverage.”

Help is on the way for New England, though. Slot receiver Julian Edelman, who has a strong rapport with Brady and is known for beating coverage, returns from a performance-enhancing drug suspension in two weeks. The Patriots also recently traded for Josh Gordon, a promising wide receiver who has missed parts of multiple seasons because of substance abuse issues.

Rob Gronkowski thinks Edelman especially will help the Patriots get back in a groove.

“I think once Edelman comes back you’re going to see a whole different game out there,” he said. “He’s a man-beater. He’s going to get open if you put man on him. Once Edelman’s back, I think the whole game changes.”

New England will have to try to piece something together on offense before then, though. They host the undefeated Miami Dolphins (yes, somehow the Dolphins are undefeated) on Sunday.

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