, the ' starting inside linebacker, will undergo surgery on Wednesday to repair a torn ACL sustained during last Sunday's 38-7 win over the Browns. Pittsburgh coach Mike Tomlin, during his weekly pre s conference, said that Robert Spillane, who replaced Bush last Sunday, will be in the starting lineup for Sunday's game against the also-undefeated Titans.The injury occurred near the end of the first half, with the Steelers enjoying a 24-0 lead. Bush sustained the injury after hitting Browns running back on an incomplete pa s. The Browns scored their first touchdown of the game four plays later.Spillane, a three-year veteran who has mostly been a special teams contributor during his two seasons with the Steelers, recording six tackles on Sunday that included a tackle of Browns tightthat resulted in a six-yard lo s. And while Spillane has only 39 regular season snaps at inside linebacker under his belt, Steelers coach Mike Tomlin is confident that his young linebacker can be an effective replacement for Bush."Spillane more than answered the bell, but we've got a great deal of confidence in him,". "He's a capable guy. Guys that make plays in special teams, that's usually a precursor to them making plays on defense. Since Kearis Jackson Jersey we brought him up in the middle of last year, he's been a consistent performer for us. So I don't think any of us are surprised from quality play from him."Tomlin also alluded to fellow backup linebackersandas players who will be part of the team's plan as it relates to replacing Bush, who last season led the Steelers with 109 tackles and four fumble recoveries. Gilbert, a sixth-round pick in the 2019 draft, has appeared in just one game this season and has yet to take a defensive snap during a regular season game. Allen, a 2018 fifth-round pick who made the switch from safety to linebacker this summer, has also never played a regular season snap at inside linebacker.On Sunday, Spillane wore Pittsburgh's defensive headset helmet after replacing Bush and will do so again for Sunday's game against the Titans,. In his first game as a starter, Spillane will try to help the Steelers' defense slow down running back, who leads the NFL with 588 rushing yards. And while the Titans po se s arguably the league's best running back, the Steelers boast arguably the league's best run defense after allowing just 331 rushing yards through five games. And while Bush was a key contributor in that succe s, the Steelers have also enjoyed big contributions from defensive end, defensive tacklesand, and inside linebackeras it relates to Pittsburgh's run defense. Pittsburgh has also received elite pa s rushing from outside linebackers T.J. Watt and, who are on pace to record a combined 30 sacks this season.The No. 10 overall pick in the 2019 draft, Bush has started in 19 of his 20 games with the Steelers. Last year, the former Michigan standout recorded 109 tackles to go with four rumble recoveries, two interceptions and two defensive touchdowns. Through four games, Bush has recorded 21 tackles this season while helping Pittsburgh get off to its first 4-0 start since 1979.Bush wasn't the only Pittsburgh defender who sustained an injury on Sunday. , who tallied three sacks during the Steelers' first four games, also left Sunday's game after suffering a shoulder injury. Tomlin said on Tuesday that Hilton's practice participation will be the team's guide as it relates to his status for Sunday's game. Kyler Baugh Jersey