MINNEAPOLIS -- A day after returning to Detroit's lineup, Magglio Ordonez is returning to Detroit. He flew back Thursday to undergo more tests on an off-again, on-again viral infection that is again in the latter position.

Ordonez played Tuesday night for the first time in nearly a week, going 0-for-4 before being lifted for defensive reasons in the ninth inning. Following the game, he complained of soreness in the area where his viral infection has bothered him since the start of the season. He called head athletic trainer Kevin Rand at the team hotel early Wednesday morning, and club officials decided soon after to send him back.

"We're looking to run whatever tests we need to get to the bottom of this," Rand said.

Rand and other team medical personnel hoped they had this solved when Ordonez began feeling better last weekend. Now, they're taking whatever steps they need to figure it out. A group of specialists will examine Ordonez on Thursday at Henry Ford Medical Center to try to form a more definitive opinion on what is fast becoming a frustrating ailment. All of the specialists who will see Ordonez have already been consulted on his situation, Rand said. They'll work under the direction of team the physician, Dr. Michael Workings.

About all the Tigers can rule out is a muscular injury. The symptoms, Rand said, are consistent with a viral infection, and they've all been intestinal. The problem has been that the symptoms keep resurfacing.

"His body has basically been a mess," manager Alan Trammell said.

Realistically, they've never been gone, though Ordonez felt well enough to play three games this season. "It was tolerable," Rand of Ordonez's discomfort. "I don't think you can say it ever totally disappeared. ... Bottom line is, we have to find out why this has continued to plague him."

No timetable is set for when he will rejoin the team, let alone when he could return to action. Team president/general manager Dave Dombrowski was optimistic Wednesday that his absence won't be long. Though test results or specialist opinions could change the outlook, the Tigers officially don't consider the disabled list an option.

"So far, there's been no indication it won't be [a few days]," Dombrowski said. "There's not anything, so far, more than anything that would keep him out a few days. We'll wait and see."

One major reason the disabled list is a long shot is the Tigers' depth in the outfield. Marcus Thames started Wednesday in Ordonez's place with Bobby Higginson available off the bench. Trammell said he'll decide his right fielder on a day-by-day basis.

"We have outfield help," Trammell said, "and if [Ordonez's absence] is two, three, four days, it's better than 15 days."

Guillen out, too: Trammell had to sit out Carlos Guillen sooner than he expected. Before taking the field for batting practice, the All-Star shortstop reported swelling and soreness in his surgically repaired right knee and was promptly bumped from the lineup.

"He had some fluid on his knee," Trammell said. "I wasn't going to take any chances."

Jason Smith replaced him at shortstop, while Brandon Inge moved from ninth to second in the batting order.

Rand characterized the swelling as minimal and was not overly concerned. "This is not unexpected," he said. "We knew coming in here on the [artificial turf] that there was a good chance that does happen, and we need to protect him. This is a long stretch. We need him playing the majority of the season."

Guillen was optimistic he could play Thursday. "The swelling's gone down," he said after Wednesday's game.

With utility infielder Ramon Martinez on the DL and Dmitri Young starting at DH, Guillen was the Tigers' only infield option off the bench.

Look who's walking: A year ago at this point, Carlos Pena was starting his challenge for the American League strikeout lead, a race for which he ended up finishing third. He's now in sole possession of the AL walks lead instead.

In a transition that actually began late last season, Pena has become one of the more selective sluggers in the league over the season's first week and a half. His nine walks entering Wednesday tied him with San Diego's Brian Giles and Arizona's Craig Counsell for tops in the Majors, though Giles later took over the lead with three walks Wednesday.

Moreover, Pena's 4.38 pitches seen per plate appearance entering the evening ranked fifth among AL sluggers, trailing other sluggers like ex-Oakland teammate Eric Chavez and Cleveland's Travis Hafner.

His power numbers aren't there yet, with a home run and five RBIs this season, but he'll gladly take the free passes.

"If I walk," Pena said, "it's a good at-bat."

To hitting coach Bruce Fields, Pena is starting to reach the understanding that many veteran sluggers eventually gain, that being an effective power hitters means learning to lay off the pitches near the zone and take a base instead of the feast-or-famine approach. Even last year, he started to show that with 70 walks, 38 of them in 66 games over the season's second half.

"They're trying to get him to swing at pitches out of the zone," Fields said, "and he's not falling for any of that. Obviously, the longer you play, the more you understand. He has a good understanding of what's going on."

That goes especially for full counts, of which Pena is drawing many as his patience improves. Two years ago, he hit .182 (8-for-44) on 3-2 pitches with 25 walks and 25 strikeouts. Last season, the hits decreased (5-for-60) but the walks increased to 34 against 33 strikeouts.

In eight full-count situations this season, he has six walks, a strikeout and a home run.

To Fields, that's the difference between being a slugger hitting sixth and hitting third or fourth.

"I think I have a good knowledge of the strike zone," Pena said. "The good guys, like Barry Bonds and Jason Giambi, would walk a lot, but when pitchers threw the ball over the plate they would damage it. What I'm trying to say is, finding the balance between aggressiveness and discipline. That's where I want to get to. I'm getting closer to the balance that I'm looking for."

If he does find that, the slugger once traded by the A's -- the team that made on-base percentage catchy -- could end up drawing 100 walks in a season.

"That would be ironic," Pena said.

Coming up: The Tigers finish up their three-game series in Minnesota with another 8:10 p.m. ET matchup. Nate Robertson makes his second start of the season for the Tigers opposite Brad Radke.