HENDERSON, Nev. -- Las Vegas Raiders linebacker Blake Martinez, who joined the team just over a month ago, announced his retirement on social media Thursday.

Martinez, 28, announced his decision four days after leading the Raiders with 11 tackles in Sunday's loss to the Jacksonville Jaguars.

"I had an amazing journey with some incredible franchises, and made lifelong friendships," Martinez wrote on Instagram. "I have chosen to step away from this career at this time to focus on my family and future passions! I am excited for this new journey and appreciate all the fans and organizations that have supported me throughout the years!"

Martinez missed practice on Wednesday for what the Raiders described as personal reasons. The team tweeted congratulations to Martinez, adding, "Good luck on your new journey."

Martinez's retirement comes in the wake of the Raiders (2-6) placing a pair of Pro Bowl pass catchers -- tight end Darren Waller and slot receiver Hunter Renfrow -- on injured reserve, and leaves Las Vegas short-handed at linebacker heading into Sunday's home game against the Indianapolis Colts.

The Raiders placed linebacker Divine Deablo (forearm) on IR on Monday, and Pro Bowler Denzel Perryman (hip, rib) and Darien Butler (hip) were limited in practice Thursday. Jayon Brown has not played since Week 4 because of a hamstring issue. The Raiders also waived strong safety Johnathan Abram, a first-round pick in 2019, on Tuesday.

On Thursday, the team did promote linebacker Curtis Bolton to the active roster from the practice squad and signed linebacker Reggie Ragland to the practice squad.

Martinez was a fourth-round pick of the Green Bay Packers in 2016 and spent the previous two seasons with the New York Giants before signing with the Raiders on Oct. 4. He started two of four games for Las Vegas and had 20 tackles, including 14 solo. In 84 career games, 78 starts, he had 13 career sacks and four interceptions.

Martinez, who had a base salary of $1.035 million, also is an avid Pokémon card collector and, according to a New York Post report last week, he sold a rare Illustrator Pikachu card known as "The Swirlustrator" from 1998 for $672,000, which would be the second-most expensive Pokémon card ever sold. The card had reportedly been valued for as much as $1.5 million a few weeks prior.