Yankees infielder Kevin Youkilis experienced a setback with his cranky lower back on Sunday, suffering a return of stiffness in the nettlesome area, and will undergo an MRI on Monday. Youkilis returned to the lineup on Saturday after six days off. He reported a fresh bout of trouble in the same area the next morning. Manager Joe Girardi gave him the day off, but that did not alleviate his fear Youkilis may land on the disabled list. "It is a little concerning for me," Girardi said before Sunday’s 3-2 victory over "I've said that all backs can be tricky. I'm a guy who has had to deal with it for a number of years. Sometimes you have no idea why it acts up." Youkilis, 34, has battled back trouble for years. He spent time on the disabled list due to similar issues in 2011 and 2012. His health is his biggest flaw as a player. Since 2010, he’s averaged 115 games a season. Youkilis felt his back tighten up for the first time on April 20 in Toronto. Girardi gave him a day off, but scratched him from the lineup on April 22. An extended period of rest only allowed him one day of action. As a right-handed batter, Youkilis balances the team’s lefty-heavy lineup. He has a .769 on-base plus slugging percentage this season. "He is important,” Girardi said. “So we have to get this right. We can't push it too fast. If there are days that he is a little stiff, we may have to back off a little bit and try again the next day."