Over the past two seasons, the Vikings have placed a higher degree of emphasis on undrafted free agents, devoting more guaranteed money to certain players in an effort to land the prospects they believe could eventually develop into key NFL contributors.

Their approach to the rookie free agent class of 2018 saw them continue on that path.

The Vikings devoted $316,000 in guaranteed money to their undrafted free agent class this spring, in the form of $98,000 in signing bonuses and another $218,000 in base salary guarantees. That's up from 2017, when they gave $85,000 in signing bonuses and $107,500 in base salary guarantees to their UDFAs.

"Last year we had seven undrafted free agents make the team," coach Mike Zimmer said at the start of the team's rookie minicamp on May 4. "We had three rookies that started and we had three undrafted players that made the team last year. It's good to get them out here."

Texas cornerback Holton Hill, who received a $15,000 signing bonus and $60,000 in base salary guarantees, received more money than any other undrafted free agent since Zimmer became head coach in 2014. Only three UDFAs — Tampa Bay's Godwin Igwebuike, San Francisco's Tarvarus McFadden and New Orleans' Deon Yelder — received more guaranteed money among UDFAs than Hill.

The Vikings gave $50,000 in guaranteed money to Southern Miss wide receiver Korey Robertson, who received the 10th-most guaranteed money of any rookie free agent. Robertson's total guarantees also surpassed the previous high figure given to a UDFA in the Zimmer era, which had been set by Tashawn Bower ($45,000) last year.

Wisconsin linebacker Garrett Dooley got $41,000 in guaranteed money, receiving a $11,000 signing bonus and $30,000 in base salary guarantees. Five players — Hill, Robertson, Dooley, safety Tray Matthews and defensive tackle Curtis Cothran — got at least $25,000 in total guarantees, while running back Roc Thomas got $23,000 and receiver Jeff Badet got $22,000.

The guaranteed amounts are still relatively minimal by NFL standards, and they certainly don't ensure a long-term roster spot — Dylan Bradley, who received $40,000 in guaranteed money last year, was cut last week to make room for David Parry. But as the Vikings continue to mine the undrafted free agent market for potential finds, it's worth noting the degree to which they're making a financial commitment to the process.