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7/3/2013 12:32 A.M. ET

Willingham elects to have surgery on knee

MINNEAPOLIS -- The Twins on Tuesday placed Josh Willingham on the 15-day disabled list, retroactive to Monday, with a medial meniscus tear and bone bruise in his left knee. Center fielder Aaron Hicks was activated from the 15-day DL to take Willingham's place on the roster.

After consulting with team physician John Steubs during Tuesday's game, a 7-3 loss to the Yankees, Willingham elected to have arthroscopic surgery on the knee to fix the torn meniscus, which will keep him out of action for four to six weeks. He's scheduled to have the operation on Wednesday; Steubs will perform the procedure.

"We both put our heads together and decided what was best," said Willingham, who has had both of his knees scoped in the past. "We knew that we had to have my knee cleaned up at some point, probably at the end of the year. So it made sense with the [two to four weeks it takes] the bone bruise to heal. So we made the decision that way."

Willingham, who has been dealing with soreness in the knee throughout the season, tweaked it on Friday. He was held out of the lineup on Saturday and Sunday but did deliver an RBI ground-rule double as a pinch-hitter on Sunday.

Willingham had been in the lineup for Monday's game against the Yankees but was a late scratch after feeling discomfort in the knee while trying to run before the game.

Willingham, 34, is hitting .224/.356/.398 with 10 homers and 37 RBIs in 70 games. He underwent an MRI on Tuesday morning that showed the meniscus tear and bone bruise.

"I know [the procedure is] going to fix the problem that's been causing me trouble," he said. "So hopefully this clears up and I can play without any pain in my knee."

Hicks, meanwhile, went on the 15-day DL with a strained left hamstring on June 10. He hit .190 with a double and two RBIs in six games as part of his rehab assignment at Triple-A Rochester.

"It's just one of those things where you can't wait to be back on the field," Hicks said. "It was good to go down there and play a few games to get ready to go. So I'm ready."

Twins agree to terms with Dominican teenager Diaz

MINNEAPOLIS -- The Twins agreed to terms with Dominican outfielder Lewin Diaz on a $1.4 million contract on Tuesday, according to Major League sources. The club has not confirmed the figure.

Diaz, 16, reached agreement with the Twins on the first day of the international signing period. He's ranked 10th overall among international prospects, according to MLB.com.

Diaz still needs to undergo a physical, and the deal must be approved by Major League Baseball before it becomes official.

Diaz is regarded as one of the top power-hitting prospects in the Dominican Republic, and his frame has been compared with that of Ryan Howard of the Phillies. The 6-foot-4, 210-pound left-handed hitter is an outfielder but could be moved to first base if he continues to grow.

The Twins have $3.9 million to spend on international free agents this year, and the $1.4 million for Diaz takes up a large chunk of that, but the Twins are expected to be active in the international market, according to general manager Terry Ryan.

"We'll be active everywhere internationally -- in the Dominican, Venezuela, Europe, Australia, Asia," Ryan said. "Every team has money earmarked for international signings, and we hope to spend it all. It won't just be one guy. It'll be a bunch."

Burton to be used in low-pressure situations

MINNEAPOLIS -- Right-handed reliever Jared Burton has been struggling recently, so manager Ron Gardenhire will try to use him in lower-pressure roles while he works through his issues.

Burton couldn't hold a one-run lead in the eighth inning of Minnesota's 10-4 loss to New York on Monday night, giving up three runs while recording just one out. He has an 11.00 ERA over his last 10 appearances dating back to June 6.

"You always try to say you'll get him in some nonpressure situations, but I don't know if there are those in the big leagues," Gardenhire said. "So we'll try to get him in some situations where it's not the eighth and a one-run lead. I talked to him, and he says his arm feels good, but he's just not putting away hitters right now. So we talked about a few other routes he can go with the way he attacks hitters."

Left-handed reliever Brian Duensing will also be used in lower-leverage roles for the time being, as he also struggled on Monday, giving up four runs over 1 1/3 innings. He has an 8.44 ERA over his last seven appearances.

"We'll give him some opportunities and try to see if we can get him feeling a little better, too," Gardenhire said.

Pelfrey on track to rejoin Twins on Saturday

MINNEAPOLIS -- Mike Pelfrey fared well in his rehab start with Class A Cedar Rapids on Monday and remains on track to rejoin the Twins on Saturday to start against the Blue Jays.

Pelfrey, who is on the 15-day disabled list, retroactive to June 19, with a strained back, gave up two runs on just two hits over six innings with six strikeouts and no walks while throwing 70 pitches.

Pelfrey was back at Target Field on Tuesday, and manager Ron Gardenhire sees no reason why Pelfrey won't be activated on schedule.

"He went six innings last night and was planning on going just four innings to watch his pitch count, but the kids were just hacking," Gardenhire said. "But it was expected by me that they would be swinging."

Rhett Bollinger is a reporter for MLB.com. Read his blog, Bollinger Beat, and follow him on Twitter @RhettBollinger. This story was not subject to the approval of Major League Baseball or its clubs.