SANTA CLARA, Calif. — The anticipation was building all week for Jared Cook’s first in-game reps with Aaron Rodgers Friday night at Levi’s Stadium.

While the Packers’ new tight end made a positive first impression during his two series with the starting quarterback, the added dimension Cook brings to the offense was evident throughout Green Bay’s 21-10 win over the San Francisco 49ers.

Whether it was Rodgers or backup Joe Callahan running under center, Cook made his presence felt in catching four passes for 54 yards in the first half alone.

Rodgers, who was making his preseason debut, fittingly completed his first pass of the game to Cook for 19 yards to convert a third-and-4 situation on the offense’s opening drive.

The two already have developed some chemistry on the practice field, but getting a chance to connect with Rodgers in an actual game provided a jolt of confidence for Cook.

“It’s being there when the quarterback needs you and building that trust,” Cook said. “I think that’s the most important thing to know they can count on you in situations like that.”

All four of Cook’s receptions on Friday night resulted in a first down, with three of them converting third- and fourth-down situations.

His blend of speed and size makes Cook a difficult target to bring down in the open field, which was evident on his first catch from Callahan in the second quarter when he stiff-armed a would-be tackler to extend a 13-yard catch.

Callahan went back to Cook two more times before halftime, finishing with a 12-yard completion across the middle on a fourth-and-5 play that started with Cook lining up wide left.

“It was great to see another big target like that,” said receiver Randall Cobb, who also had three catches for 30 yards.

“He’s great off the line. He does a great job of catching the ball and making defenders miss. That’s something that’s going to add to our offense and another piece that defenses have to worry about.”

This is an important time for Cook, who’s steadily picked up Green Bay’s offense but is still the only outsider in a sea of homegrown offensive skill-position players.

That’s why he appreciated Head Coach Mike McCarthy keeping the offense on the field on four fourth-down situations in the first half. The Packers converted on three of them.

“I think that it was really good Coach let us do that because it gives you exposure to certain situations and dire situations that you can see,” Cook said. “I think it was a good thing that he let us play a little bit.”

Packers receiver Jordy Nelson didn’t play against the 49ers but continued his pregame routine and appears to be on track to return for the regular-season opener in Jacksonville on Sept. 11.

Several players inside the postgame locker room expressed excitement about the possibility of pairing Cook with the returning Nelson, Cobb and rest of the offense’s weapons.

His debut provided a small sample of the type of mismatches he can help create for defenses, causing defenses to pick their poison with one-on-one matchups.

“That’s kind of how offenses are built is to help each other get open, trying to pull coverages in certain directions to where it opens up the next man behind you,” Cook said. “I feel like I did that. I feel like I can definitely help in this offense with that.”

Along with his receiving production, Cook showed what he could do as a run-blocker, sealing the linebacker to open the outside for Eddie Lacy on a 21-yard carry.

At the same time, Friday’s game gave him some areas to work on. He had a holding call in the first quarter and bumped into Callahan during his dropback, causing a fumble that the quarterback recovered.

However, that’s what the preseason is for and Cook is grateful for the chance to work out some of the kinks of before facing the Jaguars.

“I’m glad it happened now,” said Cook with a laugh. “It’s something to learn from. There’s so many things I have to understand in this offense and just getting better at it. That’s all it is. It’s about reps and getting better at it.”

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