Drevno went to high school in California and then played offensive line at Cal State Fullerton. He then ended up as a graduate assistant there, moved to Montana State as the tight ends coach, coached running backs for a while at Montana State and UNLV, and then settled in as an offensive line coach once he got to San Jose State in 1999. After spending a year with the Spartans, he became Idaho's offensive line coach before becoming the University of San Diego's offensive coordinator/offensive line coach from 2003-2006 under Jim Harbaugh. Drevno followed Harbaugh to Stanford to coach tight ends (2007-2008) and the offensive line (2009-2010). He followed Harbaugh once again to the San Francisco 49ers for the 2011-2013 seasons, finally leaving Harbaugh's side for the job at USC this past year.
Drevno helped produce some studs on the offensive line at Stanford and San Francisco. Center Chase Beeler was a First Team All-American in 2010 at Stanford, and the offensive line was #2 in sacks allowed in both 2009 and 2010. Then in 2012 at San Francisco, all five of the 49ers' offensive linemen were picked for the Pro Bowl. The 2013 season saw left tackle Joe Staley and offensive guard Mike Iupati get picked for the Pro Bowl. Meanwhile, running back Frank Gore had at least 1,128 yards and 8 touchdowns in each of Drevno's three seasons in San Fran. Kendall Hunter also had some pretty decent numbers as Gore's backup, although Gore carried the load each year.
This season USC is #68 in the country with 160 yards/game on the ground, and they're #87 with 3.99 yards/carry. Those numbers are not particularly impressive, but starter Javorius Allen had 1,489 yards, 5.4 yards/carry, and 11 touchdowns, while backup Justin Davis averaged 4.6 yards/carry and scored 4 times. That overall rushing number was dragged down significantly by USC allowing 32 sacks, which was #101 in the nation. The Trojans had the 36th-most pass attempts (460) and a quarterback who's not particularly mobile (Cody Kessler), so those things factor in, but the numbers still aren't great.
On the recruiting end, Drevno had reeled in a couple offensive linemen for USC that had not been offered by Michigan. Another commit is none other than Powder Springs (GA) McEachern offensive tackle Chuma Edoga, who expressed strong interest in Michigan but was never offered. Otherwise, Michigan and USC didn't cross paths very often in the 2015 class. Michigan could use another offensive lineman in this class, and Edoga might be a sensible option.
I think this is a pretty good hire for Michigan. Harbaugh and Drevno know each other well, and they've had success together previously. Drevno can point to his time and accomplishments in the NFL, and he can also use his west coast connections in recruiting. This would seem to eliminate Harbaugh's offensive coordinator in San Francisco, Greg Roman, from contention for a job at Michigan. Roman has been mentioned as an interview candidate for a couple of the open jobs in the NFL.