CLEVELAND - Scott Diamond went undrafted out of Binghamton University in New York and had to prove himself in the Coastal Plain (Summer Collegiate) League before finally signing a pro contract with the Atlanta Braves in 2007.

He never ranked among the Braves' best prospects as he climbed through their system, but Twins scouts liked the lefthander's composure and the downward plane on his pitches when he finished the 2010 season with Class AAA Gwinnett.

That December, after the Braves decided not to protect Diamond on their 40-man roster, the Twins selected him in the Rule 5 draft. They then worked a trade with Atlanta, giving up relief prospect Billy Bullock, in order to send Diamond to the minor leagues last year.

Those moves look pretty shrewd for the Twins now, as Diamond delivered another strong performance in Sunday's 6-3 victory over the Indians at Progressive Field, improving to 4-1 with a 1.86 ERA.

With baseball's annual amateur draft beginning Monday, Diamond is a reminder that even after 40 rounds -- or 50, when Diamond was coming out of school -- good players still slip through the cracks.

"He's come out and pitched well every single time," Twins left fielder Josh Willingham said, as the team celebrated its fifth victory in six games. "He's throwing strikes, and he gives you a chance to win every time he throws, and that's really all you can ask for."

Sunday marked the third time this year Diamond has pitched seven innings -- something the rest of the team's starters have done four times -- and the three runs he gave up were unearned.

The Twins grabbed an early 3-0 lead with RBI from Joe Mauer, Justin Morneau and Alexi Casilla. Cleveland capitalized on two errors by shortstop Brian Dozier to pull within 3-2 in the fourth, but Diamond didn't let the Indians score again until the Twins had stretched the lead to 5-2 in the seventh on RBI by Willingham and Ryan Doumit.

Once again, Diamond wasn't overpowering. The Guelph, Ontario, native threw 53 fastballs that averaged 89 miles per hour, and none of them produced a swing-and-miss. He finished with two strikeouts and no walks.

But Diamond clearly has his composure back -- something that went missing last year, as he went 5-19 with a 5.44 ERA in 30 combined starts for Class AAA Rochester and the Twins.

"Finishing up in Gwinnett [in 2010], I definitely felt like I had a good rhythm and a good idea of what I was trying to do," Diamond said. "I was working down in the zone really well. Last year ... I put a lot of pressure on myself to live up to that Rule 5 draft. This year, I've just tried to take it a little easier, take it one step at a time and not let things fluster me."

Diamond was 4-0 with a 1.07 ERA in four starts for Rochester before the Twins promoted him last month. Minnesota was 7-21 heading into Diamond's first start on May 8, and since then, they have gone 13-12.

The Twins are 8-3 when Diamond and fellow Rochester call-up P.J. Walters start, and 12-30 when anyone else takes the mound.

"You look out on the mound, you can't tell if they're up five runs or down five runs," Mauer said. "They're just kind of calm, cool and trying to focus on making that next pitch. So I've been real impressed with both those guys."

Joe Christensen • jchristensen@startribune.com