Rondon was named the closer before spring training began after the Tigers did not re-sign Jose Valverde and did not acquire anyone else this offseason.
Rondon, who had never thrown a pitch at the major league level, struggled with control early in the spring and was taken out of the relieving rotation to work on mechanics.
After side sessions to improve technique, Rondon seemed to have fixed what ailed him and had a better second half of the exhibition season. Fears returned about his capabilities when he was shelled by the Philadelphia Phillies the first time the Tigers used him in back-to-back games.
In 13 appearances this spring, Rondon was ineffective.
Pitching 12.1 innings, he gave up 17 hits while walking nine for a WHIP of 2.108. Hitters tattooed him for a batting average of .327 and an ERA of 5.84.
The Tigers will instead go with a committee likely to consist of Al Alburquerque, Octavio Dotel, Phil Coke and Joaquin Benoit, according to Knobler.
Coke closed in the American League Championship Series after Valverde blew a four-run lead in Game 1 to the New York Yankees, while Dotel has been a short-term closer for several other teams.
The Tigers—who tried all winter to trade for a closer—will likely shop Rick Porcello around again and also have shopped middle infielder Ramon Santiago in recent days (via Buster Olney).
The best-case scenario is that one of the pitchers in the committee can win the job full-time while Rondon learns in the minors.
The other scenario is that the Tigers get desperate and make a quick trade.
Whatever the end result, exposing their Achilles' heel to the rest of the AL is not the way they wanted to start the year.
Statistics via Baseball-Reference.com current through Thursday, March 28.