For the first quarter of the season, the Spartans could consistently rely on their ability to defend the rush. But over the past three games, MSU's interior defense has struggled to hold its own at the point of attack. It's been one of many reasons for the Spartans' three-game slide following a 3-0 start. 

This weekend, Michigan State will welcome one of the best rushing teams in the nation, Iowa, to Spartan Stadium. To compete with the Hawkeyes, the pressure is on the Spartans' rushing defense to return to earlier form. 

When the Smith era started hot and MSU won its first three games, defending the run was the main key to success. Over those three games, MSU's opponents combined for just 2.2 yards per carry and one rushing touchdown.  

"I feel like it's just Michigan State football overall to stop the run," sixth year defensive lineman Khris Bogle said after practice Wednesday. "That's the first thing in the game, you have to stop the run."

This stretch earned Spartans the 14th-ranked rushing defense in the nation entering their bout against Boston College. Then things began to spiral against BC, Ohio State and Oregon. 

MSU's top 15-ranked rushing defense quickly turned into the 59th nationally in the span of three weeks.  Opposing team numbers have shot up to 4.7 yards per carry with six rushing touchdowns. 

While the rushing attack from Boston College and Ohio State was slow and methodical, the pinnacle of MSU's run defense struggles came against the Oregon Ducks, who ripped off long run after long run against MSU. Oregon running back Jordan James couldn't be contained by the Spartans as the Ducks ran for 213 yards on the night. 

"Obviously, the last two games exposed some of the things that we need to continue to get better at," defensive line coach Legi Suiaunoa said Wednesday. "We just gotta be able to play with better technique and then be detailed. That's the difference in terms of us playing at that level."

The success of MSU's opposing running backs can be attributed to many areas, primarily lack of defensive line gap penetration and missed tackles at the second level. Chunk plays against the Spartans have been more common.

Through six games, MSU's opponents have rushed for ten yards or more 24 times. 18 of them came in the past three games. Heading into a matchup with Iowa, this poses an issue for MSU. The Hawkeyes have had a hard-nosed, run-centric identity year in and year out. They're currently ranked 13th in the nation in rushing offense. 

Junior running back Kaleb Johnson has been the star and main contributor to Iowa's backfield. The 6-foot-5, 225-pound back is a massive player to bring down and is one of the best ball carriers Michigan State will face this season. 

Johnson currently sits second in the nation in rushing yards (937), third in yards per carry (7.9) and fourth in rushing touchdowns (12). 

"It starts with stopping the run," Smith said Monday. "They have a nice back, he's not easy to tackle. So going back to team defense, we'll need multiple guys to the ball to bring this guy down."

The patient Johnson has it all: power, speed and elusiveness. Not only has his skill set made him a prolific rusher in college football; he's done it behind one of the best run-blocking offensive lines in the Big Ten. If the Spartans hope to end their three-game losing streak, reverting back to their first three weeks of rush defense will be crucial. 

The Spartans and Hawkeyes will square off on Saturday, Oct. 19 at 7:30 p.m. at Spartan Stadium. The game will be streamed exclusively on Peacock.