The Red Sox made the four moves while still waiting on the results of Wakefield's bone scan and CT scan. The veteran knuckleballer left Monday night's game after only four innings due to upper back pain.
"They did rather extensive tests," skipper Terry Francona said following Tuesday night's game. "They want to have some other doctors review those tests, hopefully [on Wednesday]. There is really nothing to [update]. We are trying to buy Wake some time to see how he bounces back. We don't have anything [to announce]. We would like to give him some time to see how he reacts. Then we will go from there."
Francona said that the team would prefer not to place the hurler on the DL at this time, adding, "You're always sore the next day. I don't think we need to place him on the [disabled list] right now. We still want to give him the benefit of the doubt.
"I don't think we're in any rush to put him on the DL because we'd like to let this settle down and see where we're at," Francona said.
General manager Theo Epstein said the club would consider several options to build its pitching depth.
"We'll just have to remain flexible," Epstein said. "You can never assume perfect health in any case. If we could wish for one thing this trade deadline season, it would be health. We'll be aggressive on the trade front and we'll explore internal options, and we'll do the best to get everyone healthy at the same time.
"We're probably in a similar boat with 18 other teams that are going to be aggressive looking for a starting pitcher in a seller's market."
As for the transactions made on Tuesday, Francona said that they were planning for them for a while, including the Harris move.
"We kind of saw it coming," Francona said of Harris, who scored the go-ahead run on Tuesday night but batted only .156 in 34 games. "Willie kind of saw it coming, and Theo was honest enough to talk to his agents back a little ways that this is a possibility. Willie filled a role on this team. He didn't play much and never started, but he did some things for us with his speed and versatility that as a manager you really love. You respect not just the way he handled this but the way he handled his job."
Francona indicated that Harris could accept an assignment to Minor Leagues just to stay in the Boston system.
"He's a great kid, and I hope there's a way where it works where he ends up coming back," Francona said. "I hate to speak out of turn, but I think he would be more than happy to be [with the] Red Sox. I think he likes it here, and we like having him here."
Lopez, a lefty specialist, compiled a 4.32 ERA in 14 relief appearances.
"Lopez didn't pitch himself out of the [bullpen]," Francona said. "There are always certain points in the season where ... having a situational guy is tough. You haven't seen the last of Lopez. He'll be back. This will be good for him, where he can pitch in circumstances when he's not pitching out of necessity but ... on a schedule."
Van Buren worked on his slider before coming up on Tuesday to begin his fourth stint with the Red Sox this season. The 26-year-old right-hander went 1-0 with a 1.48 ERA and 12 saves this year for Pawtucket.
"We know he'll take the ball multiple innings and back-to-back days in case we need that," Francona said.
The biggest immediate impact could come from the addition of Pena. The slugger underwent surgery on his left wrist on June 1 and played 12 games with Pawtucket before being activated on Tuesday.
"He was in a situation when he first got here where he wasn't playing a lot," Francona said. "Then he got a chance to play and really helped us. We're going to run into a stretch here [over] the next four or five days where we're going to face four left-handers. There's going to be a chance for these guys to play a little bit. We'll mix and match and give guys a rest when it's appropriate and keep guys sharp as much as possible."
Pitching in: David Wells is tentatively scheduled to throw a simulated game on Wednesday morning prior to the series finale with the Royals. If that goes well, Wells will throw another session against live batters in Seattle, either Friday or Saturday, depending on the field availability. Keith Foulke will throw another side session on Wednesday as he continues to build strength in his right arm. Since both have resumed throwing, they are expected to travel with the team on its upcoming West Coast swing through Seattle and Oakland.
Coming up: The Red Sox send Josh Beckett (11-5, 5.12 ERA) to the mound for the 1:05 p.m. ET series finale with the Royals, who counter with lefty All-Star Mark Redman (6-4, 5.38).