"That's where you see his experience come in play," manager Eric Wedge said of the right-hander pitching in tough situations. "You can tell this guy pitched for quite a while over in Japan. He doesn't get rattled in those situations. He really settles down, he just works to execute pitches, doesn't get caught up in the situation, just basically works on what he can control."
Iwakuma will go for his third straight win on Wednesday at Safeco Field against the Indians as the Mariners look for their eighth consecutive win.
On Friday against the Twins, Iwakuma went seven innings, allowing just one run on four hits to improve to 3-1 with a 2.37 ERA over his last six starts.
"He's consistently been better throughout the course of this year. You see more velocity, you see more at the end of his pitches. He has a great deal of confidence in both that slider and that split-finger. Drops that big breaking ball in there from time to time as you saw him do that later tonight," Wedge said after his last start. "He's pitching with a lot of confidence, but his stuff's definitely improved."
Meanwhile, Zach McAllister will be on the hill for the Indians, looking for his sixth win of the season.
The right-hander took a no-decision in his previous start, allowing four runs on eight hits in six innings of work against the A's to continue his streak. He has not allowed more than four earned runs in any of his 14 starts this season.
However, McAllister was still upset with his performance and inability to get a win after Cleveland gave him a 4-0 lead in an eventual 6-4 loss.
"Every pitcher wants to put a zero and get the guys back in and get some more runs and keep the momentum," he said after the outing. "It's frustrating when you are not able to do that."
Indians: Tomlin to have Tommy John surgery
Following a consultation with Dr. Lewis Yocum, Cleveland announced on Tuesday that pitcher Josh Tomlin will undergo Tommy John ligament-replacement surgery on his right elbow.
The procedure will be performed by Yocum on Wednesday in Los Angeles with the estimated timetable for recovery from 12-18 months.
"It's something that he needed to get done," Indians manager Manny Acta said, "in order for him to be able to compete the way he was able to compete in the past."
Tomlin went 5-8 with a 6.36 ERA in 21 appearances this season, a noticeable difference (12-7, 4.25) from his first full season in 2011.
Mariners: Saunders hitting stride
Center fielder Michael Saunders has been one of the biggest reasons for the Mariners' recent turnaround at Safeco Field, where the team has won 14 of its last 15 contests.
Saunders is batting .284 (21-for-74) with four home runs and 10 RBIs over his last 19 games at Safeco. Those numbers are a sharp contrast to Saunders' performance for the first 35 home games, in which he hit just .182 with one home run and four RBIs.
"Baseball is a process," Saunders said. "I just have to believe in my process. I know I'm going to go through ups and downs. You try to limit them, but baseball is a grind. It was a slump that was longer than I'd hope for, but everybody is going to go through them. You just have to have a good attitude and know you're going to come out of it."
The Mariners have outscored their opponents 59-24 in the first two frames since the All-Star Game, which leads the Majors.
Indians left-hander Rafael Perez (on the 60-day disabled list with a left lat injury) suffered a sprained right ankle in his most recent Minor League rehab appearance. Head athletic trainer Lonnie Soloff remains optimistic that Perez, who has been sidelined since late April, will pitch again for the Indians this season.