SEATTLE -- General manager Jerry Dipoto promised the Mariners would be active in the trade market in August, and he wasted no time backing that up, as Seattle acquired "switch-pitcher" Pat Venditte from the Blue Jays and right-handed reliever Arquimedes Caminero from the Pirates on Saturday in exchange for players to be named later.
Though the non-waiver Trade Deadline passed on Monday, clubs can still acquire players who are placed on waivers. The Mariners claimed both Venditte and Caminero and worked out deals that will be finalized by Sept. 1 with either one or two prospects going to Pittsburgh and another to Toronto. Players acquired by Aug. 31 are eligible for postseason rosters. Right-handed relievers Blake Parker and Donn Roach were designated for assignment to make room on the 40-man roster.
Parker's move also opened up a spot on the 25-man roster for starting pitcher Taijuan Walker to be activated off the 15-day disabled list for Saturday's 6:40 p.m. PT game against the Angels, since Caminero won't be able to join the team until Sunday. That means another roster move will be coming Sunday to open a spot for Caminero on the 25-man roster.
Venditte was assigned to Triple-A Tacoma. He is one of the more-interesting stories in baseball, as he uses his left arm to throw against left-handed hitters, then switches to the right arm to face righties. He's been throwing with both arms since he was a child, uses a mitt that can be transferred to either hand, and last season he became the first "switch-pitcher" to perform in the Major Leagues since Greg Harris in 1995.

"Pat is, first of all, a great makeup guy," Dipoto said. "He's pretty athletic, and obviously the nuance of switch-pitching is interesting. What we like most is the way he matches up against left-handers.
"After moving [Mike] Mongtomery to the Cubs and dealing with some injuries, Pat gives us a nice alternative as a left-on-left matchup. I don't know if he'll join us in five days or a couple weeks, but we'll see Pat Venditte this year, and he'll play a role in left-on-left matchups."
Venditte pitched eight games for Toronto this season with a 5.19 ERA in 8 2/3 innings, while posting a 2-1 record and 4.37 ERA in 25 outings for Triple-A Buffalo, including two starts.
Venditte drew considerable attention when he made his Major League debut with the A's last year and compiled a 4.40 ERA with a 2-2 record in 26 relief appearances. Per MLB rules, Venditte must indicate to the umpire which arm he's going to throw with prior to facing each hitter, and then stick with it through that at-bat.
Caminero, 29, was 1-2 with one save and a 3.51 ERA and 1.659 WHIP, with 32 strikeouts and 22 walks in 41 innings over 39 relief appearances with Pittsburgh. His ERA stands at 2.13 with 19 strikeouts in his last 21 outings since May 24, and he's regarded as a quality power arm with a fastball that can touch 100 mph, but has dealt with command issues at times.
"He's one of the hardest throwers in baseball, with an average fastball of 98 mph," said Dipoto. "The appeal of having another big-time power arm down there was real. He's had periods in his career where he's battled his control, and he got off to a rough start this year. But since the first of June, he's been lights out."
In parts of four Major League seasons, the Dominican native is 6-4 with a 3.86 ERA with 125 strikeouts and 58 walks in 135 1/3 innings over 131 games, all in relief. He pitched for the Marlins in 2013-14 and spent the past two years with the Pirates.
The 6-foot-4, 245 pounder is under team control through 2020.
Parker, 31, pitched in one game for the Mariners, as he threw a scoreless inning of relief against the Red Sox on Thursday in his first Major League appearance since 2014. Parker had 19 saves and a 2.72 ERA in 38 appearances for Triple-A Tacoma, and he previously spent parts of three seasons with the Cubs before dealing with an elbow injury last year.
Roach, 26, was 2-0 with an 8.44 ERA in four relief appearances over two stints with Seattle this season. The Mariners now have 10 days to trade, release or outright the contract of Parker and Roach to the Minors.