49ers lose freshly-signed Vance McDonald for season

As if their 12-game losing streak wasn’t enough, the San Francisco 49ers returned to practice Tuesday without starters Joe Staley, Daniel Kilgore, Torrey Smith and Ahmad Brooks.

A sputtering offense — particularly in the second half of games — is one compelling reason behind the 49ers’ season-long downfall after a 28-0 blowout win over the Los Angeles Rams in Week 1.

But the absence of Brooks certainly won’t help, even though he was unable to take down New York Jets quarterback Bryce Petty on a key fourth-quarter two-point conversion.

Just days after signing tight end Vance McDonald to a three-year, $19.7 million contract, the 49ers lost him for the season, placing McDonald on injured reserve Monday following a shoulder injury in the first half of the 49ers’ 23-17 overtime loss to the Jets.

If McDonald remains on the 49ers’ 90-man roster until April 1, 2018, all $3.7 million of his 2018 salary will become fully guaranteed. Whether or not he becomes a productive tight end will rest on his ability to stay healthy.

49ers offensive coordinator Curtis Modkins ran through McDonald’s replacements:

“Well, we’ve played a number of tight ends this year. [TE] Garrett Celek will play and [TE] Blake [Bell] will play and we’ll see what happens with [TE Je’Ron] Hamm.”

Modkins also praised 49ers quarterback Colin Kaepernick as a professional on the field who shows up to practice with a strong-willed attitude because he wants to help his team win.

49ers defense coordinator Jim O’Neil explained how his defense was able to get pressure against the Jets:

“We schemed up some stuff against their protections which we could take advantage of. We knew we had to give [Jets QB] Bryce Petty some different looks. … They got the quarterback on the ground, which was good. That hasn’t always been the case where we’ve have free runners and we didn’t finish a play or whatever. The guys did a pretty decent job finishing this past game.”

O’Neil also commented on the overall performance of 49ers linebacker Aaron Lynch in his first game back after suffering a high-ankle sprain on Oct. 23 against the Tampa Bay Buccaneers:

“Solid. Probably what you expect for his first game back. He hasn’t played football in a long time. So, he did some good things for us in our sub packages. We hope we can build from that going into his second game here.”

Kaepernick also had praise for the defense:

“Our defense was out there. [LB] [Navorro] Bowman came up with a pass. … We have all the top things in the world in our defense and they come up huge for us in certain situations.”

On another positive note, 49ers defensive lineman DeForest Buckner played all 87 snaps in Sunday’s game. Buckner leads all NFL interior defensive linemen in plays this season, despite sitting out the Week 5 loss to Arizona with a foot injury.