The Red Sox will look to avoid their first four-game slide of 2013 on Tuesday night when they face Hisashi Iwakuma, who has been vulnerable during his four-game winless stretch.Boston (54-37) fell to 1/3 on this 10-game trip with an 11-4 loss to Felix Hernandez on Monday. Hernandez, second in the AL with a 2.69 ERA, gave up two runs over seven innings.It may not get easier against Iwakuma (7-4, 2.60 ERA), the only pitcher in the league with a better ERA than his teammate. That mark, though, has risen from 1.79 during his last four outings, with the right-hander going 0-3 with a 5.54 ERA in that span.Iwakuma has yielded exactly four runs in each start of his winless streak, pitching six-plus innings Thursday as he was charged with a 5-4 defeat at Texas. His 3.86 ERA in July is his highest in any month, and he has never faced the Red Sox.Boston manager John Farrell is unsure whether he will have Jacoby Ellsbury or Shane Victorino in the lineup after both sat out Monday.Ellsbury is batting .389 during a 17-game hit streak and leads the majors with 36 steals. The center fielder suffered a left wrist injury in a 3-0 loss to the Angels on Sunday."We're hopeful that this is something that will respond to treatment," Farrell told the Red Sox's official website. "If it doesn't, certainly, every test at that point would be taken."Victorino has sat out two straight games with a hamstring injury and remains day to day.Seattle (40-49) entered play Monday averaging 3.7 runs for the second-worst mark in the AL. It reached double digits in runs for just the second time all year in its fifth victory in seven games.Raul Ibanez homered and the bottom third of the lineup went 7 for 12 with six RBIs as the Mariners fell just shy of their biggest outburst of the season -- a 12-2 win over the New York Yankees on May 15.The 41-year-old Ibanez has homered eight times in his last 13 games, batting .364 with 15 RBIs in that span."I'm 41," he said. "You can't play this game forever. I used that approach. Hopefully, I can share that approach with the younger guys, telling them, 'Hey, time goes by really fast. Enjoy this.'"The Mariners have yet to face Boston rookie right-hander Allen Webster (1-2, 7.88), who will make his sixth start after earning his first victory in his last one.Webster, who is in his third stint with the Red Sox this year, allowed a season-low two runs over six innings of an 8-2 win over San Diego on Thursday."I think at each passing start here at this level he starts to get his feet underneath him," Farrell said.