Sources: Ravens RB J.K. Dobbins to have knee scoped, out 4-6 weeks 3:53 PM ET Jamison HensleyESPN Staff Writer Close University of Maryland graduate Lives in the Baltimore area with his wife and son OWINGS MILLS, Md. - Baltimore Ravens running back J.K. Dobbins' long road back from a significant knee injury hit another bump. Dobbins, the Ravens' No. 1 back, is expected to undergo arthroscopic surgery on his left knee next week that will sideline him four to six weeks, sources told ESPN's Adam Schefter on Friday. He did not practice all week after not playing in the second half of Sunday's 24-20 loss to the New York Giants . The Ravens (3-3) will rely on Kenyan Drake , who became the first Baltimore running back to produce 100 yards rushing this season, and a growing backfield for at least the next month. Justice Hill , who leads Ravens running backs with a 6.6-yard per carry average, is back for Sunday's game against the Cleveland Browns after missing the last two games with a hamstring injury. Gus Edwards could also be activated off the physically unable to perform list after practicing the past two weeks. Editor's Picks Humphrey: Ravens are 'pressing,' need to 'relax' 10h Jamison Hensley Lamar Jackson trying to do too much to fix Ravens' late-game woes? 3d Jamison Hensley Ravens add WR Jackson, hoping for deep threat 2d Jamison Hensley 2 Related "Once you get him started and heading downhill, he's really effective," Ravens coach John Harbaugh said of Drake earlier this week. "He has some speed and some explosiveness." This is another tough blow for Dobbins, who was sidelined all of last season after injuring his knee in the preseason finale. He said he tore his ACL, LCL, meniscus and hamstring. After missing the first two games this season, Dobbins returned on a limited snap count and didn't look like he was at full strength. He averaged 3.5 yards on 35 carries in four games (123 yards). Last week, Dobbins acknowledged that it was "super hard" not playing in the fourth quarter of a 19-17 win over the Cincinnati Bengals on Oct. 9. He then sat out the entire second half after hurting his knee Sunday at the Giants. "J.K.'s knee tightened up on him; he just didn't feel like he had that explosiveness in the second half," Harbaugh said earlier this week. "I think he might've landed on it at some point." A second-round pick in 2020, Dobbins was an immediate impact player, leading all NFL running backs in rushing average (6.0 yards per carry) and setting a Ravens rookie record with nine touchdowns. Now, Dobbins won't be back for the Ravens until December at the earliest. This season, Baltimore running backs have totaled 458 yards rushing, which ranks 25th in the NFL.