Quarterback Alex Smith has been ruled out for Sunday's game because of a calf injury, head coach Ron Rivera announced Friday. Dwayne Haskins Jr. will start against the Seattle Seahawks.

Smith, who left the San Francisco 49ers game in the first half, was hopeful he would be able to play in Week 15. Even if he was not able to practice this week, he and Rivera both felt comfortable with him starting Sunday if he was healthy enough.

However, when Smith went through some of the movements he would have to do in the game, Rivera said he still felt tightness, so the team decided not to push him any further.

"For me, it just boils down to being honest with myself," Smith told reporters Wednesday. "I'm going to do everything I can all week from a treatment and rest standpoint, mentally preparing to get ready. Certainly, there is a point obviously here as the week goes on where decisions have to be made. For me, it's just about being honest. Either you can or you can't."

In relief of Smith against the 49ers, Haskins completed 7-of-12 passes for 57 yards and led the offense on a field goal drive to begin the second half. There were also some inaccurate throws, but Haskins did not commit a turnover as Washington held on for a 23-15 victory.

Rivera said after the game that the second-year signal-caller is continuing to show growth and highlighted his first couple of throws when he made quick, smart decisions and showed poise.

Just like any other position, Rivera said the quarterback situation is a "next-man up mentality." Haskins has not started since Week 4, but the team believes he can give it a chance to beat the Seahawks at FedExField and extend its winning streak to five games.

"This is a guy that's next, this is a guy that we believe in, this is a guy we kept around because we see something," Rivera said. "And you do that so when he goes out there, 'Heck yeah, we believe in him' because we believe has the athleticism, the ability, and I've always said he's got an NFL arm, he really, truly does."

Offensive coordinator Scott Turner said that he is in constant communication with Haskins, and during the 49ers game Turner told him, "Hey, I believe in you. I told you these opportunities are going to present themselves at some time. Here it is. Let's go finish this game and win it."

Since Haskins lost the starting quarterback job after Week 4, Turner said he has seen Haskins make the biggest strides in terms of his preparation. Turner has noticed Haskins shadowing Smith and modeling his preparation, which is the best course of action considering Smith has had immense success after enduring similar struggles to Haskins early in his career.

"Having somebody like Alex in the room with me is a great example," Haskins said. "He comes to work every day with his hat on it. He grinds and he never complains. He's somebody I look up to and now he's been helping me a lot throughout this whole process. He's been through stuff like this before, so he's been a great person to lean on throughout this time."

Haskins, the 15th overall pick in the 2019 NFL Draft, knows he is not a finished product by any means. He wants to be as great as the quarterbacks he watches on TV, and that requires an unwavering obsession to improve.

That is why he has been staying at the team facility later and throwing with former practice squad players on his own a few days per week. He wanted to have as many reps as possible so that when his opportunity did come again, he would be ready to show the coaching staff that he can be a reliable quarterback and leader for this franchise.

"This is the most adversity I've faced since coming into this world," Haskins said after the 49ers game. "I lean on a lot of people, a lot of mentors, family, close ones. I prayed and I prayed again. I'm just glad that I'm able to be here right now and tell you guys that I'm thankful. That's all I care about right now."

Haskins' next test will come Sunday against the Seahawks' putrid pass defense, which is allowing nearly 300 yards per game. Rivera said Haskins is "working hard on the things he needs to work at -- he's doing a nice job with it" -- and that the game plan will be tailored toward his skillset. So far this season, Haskins has completed about 61% of his passes for 990 yards and four touchdowns compared to three interceptions.

"Coming in here, with the things that have happened, it's unfortunate," Rivera said. "But life is hard. So what? Get over it, put your best foot forward, and that's what I'm doing."